List Of News

Spatio-temporal control of catecholamine neuromodulation of hippocampal pyramidal cells: from mechanisms of neuromodulator release to receptor signaling and trafficking (SpaceNeuroModule)

Scientific abstract

Chemical neurotransmission has been classified into fast neurotransmission and neuromodulation. Fast chemical neurotransmission, used by a majority of neurons in the central nervous system, is spatially restricted, thanks to a tight spatial control of neurotransmitter release at the active zone, the presence of cognate post-synaptic receptors and powerful recapture systems. In contrast, neuromodulation arises from a small number of neurons mediating slow communication to widespread neuronal networks. The sparsity of neuromodulatory synapses and the absence of direct ionotropic receptor signaling hampered our ability to resolve neuromodulation mechanisms at the micrometer and millisecond scale. In the project SpaceNeuroModule, we will address this question at noradrenaline projections in the hippocampus. We will use state-of-the art synaptosome sorting, proteomics, correlative cryo light and electron tomography (cryoCLEM), receptor interactome profiling, live cell fluorescence imaging and electrophysiology in vitro and ex vivo. We have defined 2 work packages to address the release of neuromodulators and the activation of their receptors at pyramidal dendrites, which regulates attention related learning and stress-related behaviors. First, we will determine the organization and dynamics of noradrenaline release sites. Second, we will assess the spatio-temporal extent of beta-adrenergic signaling in post-synaptic compartments. This research program will enable the formulation of design principles for neuromodulatory systems which will be tested further in disease models.

Lay abstract

The brain is composed of neurons which connect each other through synapses. A neuron sends neurotransmitter molecules to a connected neuron which captures them with specific receptors. Because a neuron receives up to thousands of synapses, some using the same neurotransmitter, each message must be sent precisely at the right place and travel minimal distance to the connected neuron and not spill over to neighboring synapses. Classical synapses are very specialized in ensuring this specific transmission with precise locations for release sites and receptors: decades of intense work from researchers around the world have discovered many of the building blocks of these synapses. A special category of neurons called neuromodulatory neurons, which comprise in particular dopaminergic neurons which degenerate in patients suffering from Parkinson’s disease, act in a different way. They do not mediate a fast signal but modulate large assemblies of neurons, even though they send molecules, in this case dopamine, to other neurons from specific sites. Because of technical difficulties such as the rarity of these neurons and their lack of fast signaling, we do not yet know how exactly is dopamine released and if specific sites are privileged, nor how receptors which are activated locally can convey the signal to the rest of the neuron. We will use state-of-the-art methods to purify neuromodulator synapses and identify new specific molecules (proteins). We will watch the structure of these sites with high resolution microscopes to understand what are the differences with classical synapses. Finally, we will image in brain tissue the release of neuromodulator and the activation and movement of their receptors to define how neuromodulation is organized and controlled in the brain.

Project: Cortical mechanisms for tactile information processing during tool use

Cortical mechanisms for tactile information processing during tool use

Scientific abstract

Tool-mediated tactile sensing is a crucial aspect of daily life. For instance, when using a fork, we can extract the food's location and texture as if the fork were part of our body. Similarly, a blind person uses a cane to perceive their surroundings and accurately estimate object locations. The brain incorporates tools like forks or canes into the “body schema” – the internal representation of our own body and its surroundings, which can be expanded by tools. This schema is believed to be maintained and constantly updated in the frontoparietal cortical network, enabling the brain to interpret somatosensory information and create a coherent tactile experience and perception of the surrounding space. However, the specific neuronal processes involved are largely unexplored.

Given the unique nature of rodent whiskers, non-neuronal, extra-somatic elements, we propose using the mouse whisker system, as a new model to study neural mechanisms in tool-mediated object localization. Furthermore, our research takes a novel approach with “prosthetic whiskers,” artificial whiskers that substitute a mouse’s innate whiskers, offering a unique opportunity to examine neuronal processes in the context of “extrinsic” tool use in mice.

The proposed study aims to test the hypothesis that the layer 1 of the primary somatosensory cortex, receiving feedback from the frontoparietal network, integrates body schema and somatosensory information during tool use. Utilizing advanced imaging and genetic manipulation, we will delve into neuronal processes from subcellular to network levels, as mice employ innate or prosthetic whiskers for object localization. This research would revolutionize our understanding of the neurophysiological underpinnings of tactile processing during tool use.

Lay abstract

How does the brain process tactile information through hand-held tools? While eating with a fork, the position and texture of the food is felt at the tips of the fork rather than at hand. Although the sensory input in this example is received at the hand surface, the tactile sensation of the food is created in the body space extended by the fork. Despite the prevalence of tool-based tactile sensing in daily life, the underlying neuronal processes remain largely unknown. This gap is due in large part to the fact that most of the neurophysiological studies of tool use are conducted in humans and monkeys, where only limited techniques and tools can be applied. To overcome this limitation, for this study, we will use mice, an animal model unconventional for the tool-use experiment. Mice have whiskers as innate tools, and we have recently developed artificial "prosthetic whiskers" that can replace them. By monitoring and manipulating neuronal activities with cellular and subcellular resolution, we will decipher the neuronal underpinnings that regulate tactile sensing during tool use. Our primary target is the layer 1 of the primary somatosensory cortex, where feed-forward somatosensory information is integrated with feedback information from higher-order cortical areas implicated in tool use. By taking full advantage of state-of-the-art techniques available for mouse research, the proposed study seeks to reveal the neurophysiological mechanisms of tactile processing during tool use in unprecedented detail. The insights gained would significantly enhance our understanding of the neural underpinnings of tool-based tactile sensing. Moreover, this research may have implications for other research areas, for example, paving the way for the design of neuroprosthetics with enhanced tactile sensing capabilities.

The Insterdisciplinary Institute for Neuroscience's very first activity report is out! The entire IINS community is proud of the work accomplished in 2023 and proud to present it to you.
Discover our key figures and highlights for 2023!
Contents:
- IINS in a few figures
- A look back at 2023
- Success stories
- Translational successes
- Technological successes

Thank you to everyone who contributed to the production of this activity report. We hope you enjoy reading it!

Activity Report 2023

Geoffrey Terral, Evan Harrell, Gabriel Lepousez, Yohan Wards, Dinghuang Huang, Tiphaine Dolique, Giulio Casali, Antoine Nissant, Pierre-Marie Lledo, Guillaume Ferreira, Giovanni Marsicano & Lisa Roux

Nature Communications. 2024-02-09

DOI: 10.1038/s41467-024-45161-x

Summary

Whether and how the endogenous activity of cannabinoid type-1 receptors impacts sensory functions in vivo is largely unknown. Here, authors show - using in vivo electrophysiology, fiber photometry, behavioral assays and pharmacology - that it impacts network dynamics in piriform olfactory cortex and the ability of mice to detect odorants.

- How was the Roux team involved in this publication?

The team performed in vivo electrophysiological recordings in both freely moving and head-fixed conditions and conducted some behavioral assays. This work benefited from fruitful collaborations within the Neurocampus (Marsicano Lab and Guillaume Ferreira) and with the Pasteur Institute.

Evan Harrell joined IINS in 2021 as part of Lisa Roux’s team. In 2023, he passed the CNRS Section 25 competition and was awarded a CNRS researcher position from January 2024. Thanks this new position, Evan Harell will now be able to continue his research on the neural circuits by which olfactory experience leads to approach or avoidance behaviors within the Lisa Roux team.

What is your background?
"I studied in 3 different countries, earning a bachelor’s degree in Biomedical Engineering from Duke University (USA, 2005), followed by Masters’ degrees in Biomedical Engineering from the University of Oxford (UK, 2008) and Interdisciplinary Life Science from the University of Paris Descartes (France, 2009). For my PhD (2009-2014), I joined Gero Miesenböck’s lab (Centre for Neural Circuits and Behaviour) at Oxford (UK) where I identified some of the molecular machinery that supports homeostatic synaptic plasticity in the Drosophila olfactory system. As a post-doc (2015-2021), I returned to Paris to study olfactory and tactile sensory processing in the teams of Brice Bathellier (Institut de l’Audition) and Daniel Shulz (Neuro-PSI)."

Why did you join IINS?
"As a post-doc, I was more and more impressed by the ease with which smells are remembered by both humans and mice. The Roux laboratory at IINS was conceived to study this phenomenon, and it turned out that many of my friends and colleagues knew Dr Lisa Roux and recommended that I contact her about joining the team. After an official visit in 2019, it was clear to me that the dynamic and interdisciplinary environment at IINS would be an ideal place to achieve my research ambitions. I officially joined the Roux team in 2021 as a pre-recruitment chair at the University of Bordeaux and in 2023, I passed the CNRS section 25 concours to become a permanent researcher starting in January 2024."

Can you tell us about your research?
"Survival behaviors like evading predators or finding food and mates can be reduced to a series of simple decisions: to approach or to avoid? Scents play a very informative role in these choices, and my research aims to determine the neural circuit basis by which olfactory experience leads to learned approach or avoidance. To understand how odor attractions and aversions are learned and drive action, I am using in vivo two-photon microscopy and optogenetics during head-fixed or freely moving odor-driven memory tasks in mice."

Which difficulties have you encountered for have this new position?
"IIt was a long and winding path. After reaching out to Dr Roux in 2018, it took 6 years to secure my long-term position in the Roux team. The competition for permanent positions in France is fierce with many highly qualified candidates, and many auditions along with a long distance family life made these past years very challenging."
Which opportunites will offer to you this new position?
"I am thrilled to have finally secured my future at the IINS in the Roux team. As a permanent researcher, I can develop long term projects like an olfactory virtual reality where mice navigate in a virtual world defined only by smells. On fixed term contracts, I was always faced with uncertainty over my future, whether from doubt about an upcoming contract extension or impending evaluation. This constant pressure forced me to focus solely on short and middle term prospects. Now, I feel much more relaxed and am free to engage in challenging projects that can have a much bigger impact."

Any advice for scientist and in particularly to a scientist who are looking for a researcher position?
"For young scientists, I think the simplest personal advice is patience and persistence. Do not let rejection demoralize you. Listen to the feedback, improve your file, and try again. From a scientific standpoint, I think the key to success in the current research landscape is collaboration. The work that I am most proud of in my career has come from fruitful interactions with fellow scientists who have broadened my perspectives and forced me to be more deliberate in presenting our results."

*Boileau, C., *Deforges, S., *Peret, A., Scavarda, D., Bartolomei, F., Giles, A., Partouche, N., Gautron, J., Viotti, J., Janowitz, H., Penchet, G., Marchal, C., Lagarde, S., Trebuchon, A., Villeneuve, N., Rumi, J., Marissal, T., Khazipov, R., Khalilov, I., Martineau, F., Maréchal, M., Lepine, A., Milh, M., Figarella-Branger, D., Dougy, E., Tong, S., Appay, R., Baudouin, S., Mercer, A., Smith, J.B., Danos, O., Porter, R., #Mulle, C., #Crépel, V., 2023. Ann Neurol. doi:10.1002/ana.26723, *co-first authors, # co-senior authors

Summary

The teams of Christophe Mulle (CNRS researcher and IINS Team Leader, University of Bordeaux) and Valerie Crepel (INMED, Inerm, Marseille) have demonstrated that localized injection of a viral vector targeting GluK2/GluK5 kainate receptors in the hippocampus is a highly promising gene therapy strategy for controlling seizure onset in drug-resistant epilepsy patients. Based on the gene therapy strategy described in the Annals of Neurology article, the Dutch company uniQure, which has acquired the start-up Corlieve Therapeutics - of which Valerie Crepel and Christophe Mulle were scientific co-founders - will launch a Phase I/IIa clinical trial in the USA to for the treatment of drug-resistant temporal lobe epilepsy.

Presentation of the article

This article is the fruit of a long-standing collaboration between Christophe Mulle and Valerie Crepel. It represents a key step in the development of a gene therapy approach for the treatment of temporal lobe epilepsy. Epilepsy, which consists in the synchronized, abnormal excitation of a group of neurons in the cerebral cortex, affects around 600,000 people in France. Temporal lobe epilepsy is the most common form of epilepsy in adults, with the affected area mainly in the hippocampus. Medical treatment, using antiepileptic drugs to normalize the hyperactivity of cortical circuits, is effective in 70% of cases. For drug-resistant forms, surgical resection is often the only option left. Against this backdrop, the two teams have developed a translational project targeting kainate-type glutamate receptors.

This project is based on the hypothesis that GluK2/GluK5-type kainate receptors localized ectopically at aberrant synapses formed by the sprouting of axons from dentate gyrus granule cells, act as detonators in triggering epileptic discharges in the hippocampus. In 2014, an initial study by these researchers demonstrated that the genetic deletion of grik2, the gene encoding the GluK2 subunit of the kainate-type glutamate receptors, or pharmacological inhibition of GluK2/GluK5 receptors, led to a reduction in the number of spontaneous and recurrent seizures observed in a mouse model of temporal lobe epilepsy. A patent had been filed indicating GluK2/GluK5 as a potential target for treating temporal lobe epilepsy.

In the "Annals of Neurology" article, the teams of Valerie Crepel and Christophe Mulle (and in his team the work carried out mainly by Severine Deforges, IR CNRS), chose to develop a strategy based on interfering RNAs to reduce grik2 gene expression locally in the hippocampus. The article describes the strategy for selecting interfering RNA sequences in cell models, and the production of a viral vector that enables expression of an anti-grik2 microRNA in hippocampal neurons. This viral vector was injected in vivo into epileptic mice. The article demonstrates the efficacy of this viral vector in decreasing grik2 expression and GluK2 levels in the hippocampus, and ultimately in reducing epileptic activity in mice in vivo. Moreover, administration of the viral vector to organotypic hippocampal slices obtained from surgically resected epileptic patients, led to the suppression of epileptiform discharges recorded in these slices.

In conclusion, localized injection of a viral vector targeting grik2 expression in the hippocampus represents a highly promising gene therapy strategy for controlling seizures in drug-resistant epilepsy patients.

The work described in this article goes hand in hand with an industrial drug development strategy that Valérie Crépel and Christophe Mulle have been pursuing for several years, with the support of Aquitaine Science Transfert, Inserm Transfer and the Kurma Partners investment fund. Valerie Crepel and Christophe Mulle were the scientific co-founders of start-up Corlieve Therapeutics in October 2019, a company that was acquired in July 2021 by uniQure, a Dutch company specializing in the development of gene therapy for neurological diseases.

In September 2023, in parallel with the publication of the article in Annals of Neurology, uniQure issued a press release (see attached pdf), announcing that “the U.S. Food and Drug Administration (FDA) has cleared the Investigational New Drug (IND) application for AMT-260, the Company’s gene therapy candidate for refractory mesial temporal lobe epilepsy (MTLE).” “AMT-260 comprises an AAV9 vector that locally delivers two engineered miRNAs designed to degrade the GRIK2 gene and suppress the aberrant expression of glutamate receptor subtype GLUK2 that is believed to trigger seizures in patients with refractory MTLE.”. Accordingly, following the gene therapy strategy described in the Annals of Neurology article, uniQure will launch a Phase I/IIa human clinical trial to be conducted in the US in early 2024.

Find out more about uniQure's press relea

Exciting event on October 16, 2023

Event co-organized by Lisa, Guillaume Ferreira and Giovanni Marsicano on October 16, 2023 with the support of the Neurocampus Department and the IdEx. Check out the program!

The team is happy to welcome a new permanent member.

Evan will bring complementary expertise to the team such as calcium imaging, Neuropixel recordings and computational approaches. His main project will focus on valence coding in olfactory circuits. Congratulation to him!

The PHRC TiM-DepisT project is a national hospital-based clinical research project. Its aim is to detect (DepisT) and treat (TiM = immunomodulatory therapy) the presence of autoimmunity in people suffering from psychiatric disorders (psychosis).

Led by Frederic Villega (CHU Bordeaux/IINS) and involving 9 University Hospitals across France, the project involves psychiatrists, child psychiatrists, neuropaediatricians and researchers. Psychiatrists Marion Leboyer from the Fondamental Foundation, Bruno Aouizerate, David Misdrahi, Sebastien Gard and Anouck Amestoy from Bordeaux Charles Perrens CHU, will be working hand in hand with researchers from Laurent Groc's IINS team (Delphine Bouchet, Olivier Nicole, Julien Dupuis, Helene Grea) and the Bordeaux CHU immunology department team (Isabelle Pellegrin, Patrick Blanco, Cecile Bordes).

The project was born in 2019 thanks to collaborative work between the research team of Laurent Groc (CNRS/University of Bordeaux), and the neuropaediatrician Frederic Villega, with the support of the Clinical Research Department of Bordeaux University Hospital.

In terms of funding, the project was supported by the the French government with the “Direction Generale de l'Offre de Soins”. The strength of this project lies both in the clinical question and in the fundamental and technological advances made by the IINS research laboratory. IINS researchers have built a diagnostic platform, coordinated by Delphine Bouchet (CNRS Research Engineer). It enables the presence of pathological autoantibodies to be detected with a high degree of reliability, which is a fundamental issue in this field. This effort began more than 10 years ago with the support of the “Fondation de le Recherche Medicale” (FRM), the Fondation “FondaMental”, and more recently, thanks to the award in 2019 of the SPARK prize from the University of Bordeaux. Thanks to the emergence of this innovative platform, the clinical project can now be rolled out with a budget of one million euros.

The project has also had a long road ahead, with submissions to many institutions (“Agence nationale de securité du medicament", ethics committees, etc.) and the covid pandemic. Nevertheless, diagnosis and treatment of the disease will be able to begin in October 2023.

The prospects for the PHRC TiM-DepisT project are therefore significant. Between 2024 and 2027, researchers plan to carry out diagnostic research on 1,000 patients. The aim is to detect and provide access to immunotherapy treatment for several dozens of them. This unprecedented system opens up a host of possibilities for the benefit of medicine, which is in the midst of a revolution as a result of the discovery of the multiple implications of autoimmunity.

Frederic Villega has a few words to say about the PHRC TiM-DepisT project :

"As a clinician at the CHU, who has been working with Laurent Groc and his team for many years, I have structured this bridge between the clinical and the technological. This enables us to transfer elements of major fundamental discoveries for the benefit of healthcare! In this way, I've been able to bring together the strengths of Bordeaux University Hospital and the IINS to build an incredibly ambitious project that will provide answers to major burning questions about the new concept of immuno-psychiatry. [...] Laurent Groc was the researcher who, with his team and his international partners, climbed the first steps of an immense edifice concerning the physiopathology of psychiatric illnesses. This project represents immense hope for all mankind. It is, of course, one of many examples of the importance of research to healthcare and the quality of life of the men and women of tomorrow. [...] The aim of this research project is to answer 2 major questions in the context of mental health care: How prevalent is dysimmunity among the many factors involved in the pathophysiology of the diagnosis of psychosis? And to what extent can these patients, with an autoimmunity, respond to immunomodulatory therapy? This project could prove to be a major global turning point in psychiatric diagnosis and treatment, offering millions of families the hope of a brighter future!

Seminar Molecular and cellular mechanisms of synapse physiology

Monday 6th November 2023

Workshop: Virtual Presynaptic Terminal

We invite you to a workshop where a collaborative team from University College London (UCL) and the University of Warwick will introduce a computational modelling framework that enables in silico exploration of the mechanisms of Ca²⁺-driven neurotransmitter release in different synapses.

Morning session 9:00 – 12:30

• Kirill Volynski: Introduction to the modelling framework with examples linking the model and experimental data.

• Yulia Timofeeva: 3D modelling of presynaptic Ca2+ dynamics, covering Ca2+ influx, buffering, and diffusion.

• Chris Norman: Modelling Ca 2+ activation of vesicular release and short-term synaptic plasticity.

• Round table: model expansion across the synaptic cleft.

Afternoon session 14:00 – 17:00

• Yulia Timofeeva and Chris Norman: hands-on training for application of the virtual presynaptic terminal model. Contact the presenters to book a one-to-one training session.

Registration before October 20: https://evento.renater.fr/survey/workshop-virtual-presynaptic-terminal-iyqqwh9v

Tuesday 7th November 2023

Seminar Molecular and cellular mechanisms of synapse physiology

Venue: Centre Broca Nouvelle-Aquitaine (Amphitheater Broca)

Program

9h30 - Maria Passafaro "Unraveling PCDH19-related pathogenic mechanisms in Developmental and Epileptic Encephalopathy 9 (DEE9)"

10h10 - Andrea Barberis 'Spatial determinants for the interactions of glutamatergic and GABAergic synapses in dendrites of hippocampal pyramidal neurons"

10h50 - Kirill Volynski "Synergistic regulation of neurotransmitter release by different synaptotagmin isoforms"

11h30 - Aude Panatier "Astrocytic EphB receptors control NMDAR functions and memory"

14h - PhD defense of Agata Nowacka "Differential contributions of pre- and postsynaptic components in tuning high-frequency short-term synaptic plasticity"

Contact

Kirill Volynski (k.volynski@ucl.ac.uk), UCL Queen Square Institute of Neurology

Chris Norman (c.norman@ucl.ac.uk), UCL Queen Square Institute of Neurology

Yulia Timofeeva (y.timofeeva@warwick.ac.uk), Department of Computer Science, University of Warwick

Put yourself in the shoes of an IINS scientist and find more about our research topic!

Video presentation of IINS

Created in 2011 by the CNRS and the University of Bordeaux, IINS is a research center that investigates brain cell communication in the healthy and diseased brain. The Institute is located on the Bordeaux Neurocampus, near to the city center. This is an open place in which we welcome scientists from around the world  as well as the General Public. Exciting discoveries and ideas are discussed throughout the year in a large number of conferences and symposium.

With nearly 200 scientists, our goal is to shed light on the fundamental molecular mechanisms underpinning brain cell communication in health and disease, aiming at paving the way for innovative therapies for major neurological and psychiatric diseases. Together, we are working on multidisciplinary projects while highlighting the development of new technologies and tools.

In a few figures, IINS counts approximately 60 publications per year, 50 international collaborations, 10 ERC grants and several patents!

At the forefront of brain research, IINS scientists decode how neuronal networks compute information from the nanoscale to the behavior level. It's a stimulating environment for academic research and biotech companies.

What about you? What are you waiting for to join IINS?!

Follow us on social networks:

- X: https://twitter.com/iins_bordeaux

- LinkedIn: https://www.linkedin.com/company/interdisciplinary-institue-neuroscience-bordeaux-iins

- YouTube: https://www.youtube.com/@iins_bordeaux

Marie-Lise Jobin is currently a post-doctoral researcher in Daniel Choquet’s "Dynamic organization and function of synapses" team. Interested in the role of the cytoskeleton in the function and structure of dendritic spines, the scientist is supervised by Anna Brachet. Marie-Lise recently obtained a permanent teaching-research position at the Institut National Polytechnique de Bordeaux (Bordeaux INP). Here, she looks back on her career.

What is your background?
"I studied biology and structural biochemistry at the University of Bordeaux. During my Master’s and PhD, I worked in many different laboratories. First, I spent three months working at the University of Guelph in Ontario, Canada. Then, for my PhD, I joined the Institute of Chemistry and Biology of Membranes and Nano-objects (CBMN) in Pessac. On completion of my studies, I spent a year as a post-doctoral fellow at the Nutrition and Integrative Neurobiology Laboratory (Nutrineuro) in Bordeaux. I then spent over three years at the University of Würzburg in Bavaria, Germany. And for the last four years I’ve been at IINS. My post-doctoral adventure will finally come to an end at the end in September 2023, and I’ll be taking up a position as an associate professor in September!"

Why did you join IINS?
"Generally speaking, I’ve always been interested in biomolecular interactions involving cell membranes. I first worked on synthetic membrane models. However, I’ve always wanted to study more physiological systems. So the neuroscience field allows me to work with systems closer to physiology, and to use my highly interdisciplinary skills. [...] Anna Brachet’s field of research on the role of cytoskeletal proteins, in particular spectrins, and their partners, in the regulation, function and mechano-transduction of dendritic spines fit perfectly my research interests. Moreover, IINS is considered one of the most recognized institutes in the field of neuroscience. Above all, IINS is part of a synergistic system, with close relations to the Bordeaux Imaging Center (BIC). It was a unique opportunity to develop my skills in cutting-edge microscopy techniques and gain access to considerable knowledge in this field!"

Can you tell us about your research?
"I’m trying to understand the role of cytoskeletal proteins, beta spectrins, in neurons, and more specifically in dendritic spines, which are the seat of neuronal transmission. My results showed that beta spectrins are co-organised on a nanoscopic scale in dendritic spines and are particularly important for the stability of these structures. Their membrane or cytoskeleton partners are all the more important in maintaining and stabilising these spectrins under the membrane and influence their nano-organisation."

As a woman in science, what difficulties have you encountered?
"My biggest difficulty has always been a lack of self-confidence. But throughout my career I’ve been lucky enough to meet scientists, men and women who have had faith in me, and who have always supported and encouraged me along the way."

Why do women need to be more recognised in the scientific community?
"It seems quite logical to me that gender diversity, or diversity of any kind, leads to better, more creative and innovative science. I can see that things are changing, slowly but surely, in the right direction, and I’m optimistic for the future!"

Any advice for young researcher?
"I’m proud to have got where I am, to have succeeded in obtaining a permanent position in academia, and to have stayed the course despite many years of not knowing what would happen and never giving up. You have to persevere. It’s often the fear of failing that stops us from moving forward, so don’t hesitate, dare to take the plunge and, above all, trust yourself."

Created in 1946 at the proposal of the eponymous US senator, Fulbright is an international academic mobility program of the US government. The aim of the program is to promote educational and cultural exchanges between France and the United States.

“In addition to the funding that will help me live there, being a Fulbright fellow in the US is really recognized and will help me develop my network and meet many academics in various disciplines. Fulbright fellow also have a mission to be ambassadors of their country, and I certainly intend to introduce to colleagues to some French cuisine specialties!”

Mathieu Letellier, Yukiko Goda

Neuroscience. 2023-06-07

DOI: https://doi.org/10.1016/j.neuroscience.2023.05.032

Summary

Astrocytes have been increasingly acknowledged to play active roles in regulating synaptic transmission and plasticity. Through a variety of metabotropic and ionotropic receptors expressed on their surface, astrocytes detect extracellular neurotransmitters, and in turn, release gliotransmitters to modify synaptic strength, while they can also alter neuronal membrane excitability by modulating extracellular ionic milieu. Given the seemingly large repertoire of synaptic modulation, when, where and how astrocytes interact with synapses remain to be fully understood. Previously, we have identified a role for astrocyte NMDA receptor and L-VGCC signaling in heterosynaptic presynaptic plasticity and promoting the heterogeneity of presynaptic strengths at hippocampal synapses. Here, we have sought to further clarify the mode by which astrocytes regulate presynaptic plasticity by exploiting a reduced culture system to globally evoke NMDA receptor-dependent presynaptic plasticity. Recording from a postsynaptic neuron intracellularly loaded with BAPTA, briefly bath applying NMDA and glycine induces a stable decrease in the rate of spontaneous glutamate release, which requires the presence of astrocytes and the activation of A1 adenosine receptors. Upon preventing astrocyte calcium signaling or blocking L-type VGCCs, NMDA + glycine application triggers an increase, rather than a decrease, in the rate of spontaneous glutamate release, thereby shifting the presynaptic plasticity to promote an increase in strength. Our findings point to a crucial and surprising role of astrocytes in controlling the polarity of NMDA receptor and adenosine-dependent presynaptic plasticity. Such a pivotal mechanism unveils the power of astrocytes in regulating computations performed by neural circuits and is expected to profoundly impact cognitive processes.

Julien P. Dupuis, Olivier Nicole, Laurent Groc

Neuron. 2023-05-25

DOI: https://doi.org/10.1016/j.neuron.2023.05.002

Read the portrait of Marine Cabillic in English and French

Marine Cabillic, former research engineer in the team of Jean-Baptiste Sibarita, looks back on her five-six years at IINS. She is now software product manager at ONI (Oxford Nanoimaging) where she is responsible for a cloud software solution. At IINS, she has implemented several software solutions, analysis pipelines, as well as biology and imaging protocols for the automation of super-resolution microscopy by localisation

What is your background?
"I have always been interested in the health field. Thus, throughout my career, I have developed tools for the acquisition and analysis of biological or biomedical images. First, I joined ISEN Brest, an engineering school also has a speciality in biomedical technologies. Then, I did my last year of the master’s degree in a work-study program at Medimaps which is a start-up company specialised in medical imaging software. When I graduated, I joined Jean-Baptiste Sibarita’s team [...] and after two years at the Institute, I did a cifre thesis with Sanofi. This was part of a partnership between Sanofi-Aventis in Paris and the Institute. Then, at the end of my thesis and six months as a post-doc, I was hired at ONI."

Why did you join IINS?
"I initially had no expertise in neuroscience. However, I had a background in health and biotechnology, with software design. Moreover, the Sibarita team is a technical team where neuroscience is not the main subject of the research project. [...] For me, IINS is very interdisciplinary and innovative, with very varied projects, tools and fields of application! IINS is internationally recognised, which allows for more collaborations and projects. I joined IINS because I wanted to work in research and innovation. [...] At the Institute, in collaboration with Sanofi, I developed an automated method, combining high-content screening (HCS) and super-resolution, capable of screening and quantitatively characterising therapeutic antibodies for immunotherapy applications. The idea was to characterise the organisation and trafficking of antibody/therapeutic receptor pairs at the membrane of T cells in 96-well plates by quantitative single molecule localisation microscopy. This was done using the HCS-SMLM platform but I also worked on single cells using super-resolution multiplane light sheet imaging (soSPIM)."

As a woman in science, what difficulties have you encountered?
"I faced a lot of technical challenges during my thesis. At the beginning, being quite isolated in terms of a project that was not neuro-focused, I did not dare to go and ask other teams for advice. Also, when the project was not moving in the right direction, I found it difficult to confront the ideas of my collaborators. But the scientific world is very collaborative, to evolve in this world, you have to open up and exchange with others. So this what I did, I openned-up and ask for help of my peers to overcome my difficulties!"

Why do women need to be more recognised in the scientific community?
"In my field, which is technical, there are very few women. So it is more difficult to get ahead. In order to achieve gender equality, it is important to promote more women who carry out research projects or technical theses in order to reach young women as early as possible. Nevertheless, year after year, I notice an increase in the number of women working in technical research!"

Professional pride?
"I have very often embarked on new projects and fields. So I had to learn to adapt. During my thesis with Sanofi, I had to learn everything about biology. And I succeeded, I ended up developing protocols for culture, transfections, immune-labelling and imaging. Before that I had never touched a pipetboy in my life. When I accepted my current position at ONI, I also threw myself into the unknown, a position of responsibility, no initial skills, in English and working from home, big challenge but I adapted!"

Any advice for young researcher?
"Go for it. Why not yourself? First author of a paper, give a talk at that conference, win that prize, try a project, or apply for that kind of job,... Have fun. Science is fun, try projects/collabs, experiments, explore avenues. Train as much as you can and attend conferences,... Get organised. Planning your research projects is a key and important point that will avoid surprises and allow you to change your strategy if necessary and at the right time. Popularise your science! The first few times are hard but you will come out better."

Engineer to automated fluidics and microfabrication approaches for multi-conditions observation of 3D biological samples

The Sibarita team "Quantitative Imaging of the Cell" is seeking an engineer to develop automated fluidics and microfabrication approaches for multi-conditions observation of 3D biological samples using the soSPIM technology.

Project description

Spheroids and organoids have emerged in the last decade as very promising biological models for applications ranging from fundamental research to toxicology assays or drugs screening. However, the difficulties to culture and image them in 3D hamper their full adoption by laboratories and compagnies. In the meantime, Light Sheet Fluorescence Microscopy technics (LSFM) have proven to be extremely efficient for 3D imaging of biological samples at various spatial and temporal scales with minimal photo-damaging effects.However, LSFM technics are usually restricted in the number of sample and/or condition that can be probed due to complex sample mounting constraints. To address those questions, we develop in collaboration with V.Viasnoffand G. Grenci teams at MBI (NUS, Singapore) a culture and imaging platform combining microfabricated micro-wells,with a single-objective-based LSFM architecture named soSPIM. This combination allows to standardize and parallelize both the culture and the imaging of complex 3D biological models, paving the way toward the use of spheroids and organoids in multi-conditions screening experiments.

In that perspective,we aim to develop new culture vessels that would allow to transform our culture and imaging platform in a multi-condition one. Those new vessels will have to allow the appropriate and timely delivery of media and chemical compounds into the 3D cultured models. Then, a dedicated process will be implemented to allow the automated monitoring of those different conditions using the soSPIM 3D imaging technology.

Missions

The candidate missions will be:

• to develop a custom fluidics system for media and chemical compounds delivery into multi-wells plates,
• to adapt the fabrication process of the JeWell devices to this multi-well plate format. She/he will also participate to the validation of the multi-conditions systems created performing toxicology assays on 3D biological models developed in the team or by collaborators.

Candidate profile

We seek a motivated, enthusiastic and independent candidate, with a strong expertise in fluidics and automation and showing an interest in biology. Complementary skills in fluorescence microscopy, and/or programming would be appreciated. The candidate will work in an English-speaking environment, in close interactions with biologist in Oncology (BRIC).

Contract

Applicants should send a CV, a motivation letter and contact details for at least two referees to: jean-baptiste.sibarita@u-bordeaux.fr and remi.galland@u-bordeaux.fr

April 2023

Caroline Bonnet1, Justine Charpentier1, Natacha Retailleau1, Daniel Choquet1,2, Françoise Coussen1*
1University of Bordeaux, CNRS, Interdisciplinary Institute for Neuroscience, Bordeaux, France; 2Bordeaux Imaging Center, Bordeaux, France

eLife. 2023-04-20

DOI: https://doi.org/10.7554/eLife.85609

Françoise Coussen, Director of research at the CNRS at IINS worked on AMPAR intracellular transport and directed this work helped by Daniel Choquet. Caroline Bonnet, PhD student, performed the experiments helped by Justine Charpentier who performed all biochemistry experiments and by Natacha Retailleau (molecular biology).

Find the explanations of the scientists of this publication

Identification of the molecular mechanisms regulating the intracellular transport of glutamate receptors: a new pathway for controlling synaptic plasticity

"The modulation of the efficiency of synaptic transmission between neurons is one of the fundamental processes of memory and learning phenomena. This regulation of the strength of synaptic transmission is largely driven by changes in the number of receptors present at the synapse. In this work, the researchers identify a new mechanism for controlling the establishment of receptors at the level of the synapse through the control of their intracellular transport.

Neurotransmitter receptors, and in particular glutamate receptors, are concentrated in synapses in front of neurotransmitter release sites. However, in the process of their biogenesis, these receptors are synthesized at the level of the endoplasmic reticulum, most of the time several hundred microns from the synapses. They must therefore be transported to the synapses. Our previous work had made possible to visualize for the first time the intracellular transport of AMPA-type glutamate receptors, responsible for the majority of the rapid excitatory transmission between neurons. These receptors are transported rapidly (1-2 microns per second) in vesicles circulating on the microtubules using molecular motors. We observed that, surprisingly, this transport was strongly regulated by neuronal activity.

In this new work, we have identified the molecular mechanisms responsible for these regulations. The cytosolic C-terminal domain of the AMPAR GluA1 subunit is specifically associated with two proteins, 4.1 N and SAP97. We analyzed how interactions between GluA1 and 4.1N or SAP97 regulate GluA1 transport and its exocytosis under basal conditions and after induction of synaptic plasticity (LTP). Our results identify differential roles of 4.1N and SAP97 in controlling the different phases of transport and membrane integration of GluA1.

This work opens new perspectives in understanding the molecular mechanisms that control the establishment and maintenance of glutamate receptors at the synapse during synaptic plasticity."

Created in 1948, the Fondation pour la Recherche Medicale (FRM) has as an aim to support and fund the public research in every medical and pathophysiologic fields.

Thus, the FRM supports more than 400 new researches conducted in the laboratories of public research and higher education organisations every year (INSERM, CNRS, INRA, CEA, Universities, Prestigious Universities, health institution, …).

Gregory Giannone (CNRS researcher and team leader “Mechano-biology of motile and neuronal structure”) and his team have just won the FRM Team Price 2023!                                                      

This price is awarded to teams proposing an innovative research program in biology with potential health applications.

Gregory Giannone’s team explains us their project:

"Adhesive and cytoskeletal structures control cell functions such as migration and proliferation. As such they regulate cell behavior during physiological processes such as development; but when altered, these structures contribute to pathologies including cancer. How assembly of adhesive and cytoskeletal structures and resulting mechanical forces are coordinated to shape cell movements and morphologies during development and cancer progression remains fundamental questions. Despite recent advances in imaging methods in multicellular environments (organoids, small organisms), a molecular understanding of these fundamental processes is still lacking. To reach this molecular understanding, we developed for the last ten years, new strategies to study integrin adhesions and actin-based protrusions at the molecular level using super-resolution microscopy and single protein tracking. We unraveled key molecular events leading to: integrins activation and mechano-sensing in healthy and cancer cells; actin assembly in dendritic spines, and in lamellipodia. However, these findings were obtained by studying isolated cells on stiff 2D substrates. In this proposal, we aim to reach a molecular understanding of cell movements and morphologies in 3D multicellular assemblies characterized by softer, confined and dynamic 3D environments. In this project, we will decrypt the mechanical and biochemical molecular rules that govern the assembly, dynamics and coordination of integrin adhesions and actin protrusions in 3D multicellular systems during two fundamental processes: (AIM 1) the formation of long-lasting macromolecular complexes in vivo during development of integrin-based muscle attachment sites in Drosophila; (AIM 2) the formation of transient macromolecular complexes supporting the ability of Small Cell Lung Cancer cells to assemble into spheroids and to migrate during metastasis. This project could help to find new and more specific therapeutic strategies against this cancer."

Congratulations to the "Mechano-biology of motile and neuronal structure" team!

Read the portrait of Mathieu Letellier in English and French

Mathieu Letellier is a CNRS researcher in Olivier Thoumine’s team "Cell Adhesion Molecules in Synapse Assembly” part of the IINS. For many years, he has been interested in the processes that control the plasticity and development of neural connections. His work has highlighted the role of  adhesion proteins and neuronal activity in the functional and molecular differentiation of synapses and in the mechanisms of plasticity and homeostasis of neuronal circuits. Recently, Mathieu Letellier was awarded a CNRS 2023 bronze medal.

What is your background?

"I have a background in cell biology and physiology through my undergraduate studies at University Pierre and Marie in Paris. Then I did my graduate studies in the laboratory ‘Neurobiology of Adaptive Processes’ with Pr Jean Mariani and Dr Ann Lohof. Finally, I joined Dr Yukiko Goda as a post-doctoral fellow, first at University College London and then at the RIKEN Brain Science Institute in Tokyo. Overall, through my academic career, I have developed a cell physiologist profile [...] and I am now expanding my skills with molecular approaches and high resolution microscopy."

Why did you choose neuroscience?

"Throughout my studies, I was fortunate to have excellent teachers. They passed on me their passion for neuroscience and the will to better understand how the brain works. Moreover, I have chosen neurosciences owing to their interdisciplinary nature. They catalyse strong interactions between people coming from various backgrounds that include cell biology as well as oncology, immunology […] but also chemistry, physics, mathematics, psychology, ethology and many more!"

Why IINS?

"I joined IINS in 2012 following my post-doctorate. At the time, I was looking for a laboratory that would allow me to pursue my research on the development and function of neuronal connections while expanding my field of expertise and knowledge. IINS appeared to be an excellent option: a laboratory in full effervescence, very attractive, open to the world and marked by interdisciplinarity! In addition to that, I had the opportunity to join Olivier Thoumine’s team in which I later obtained a permanent CNRS position. In my opinion, this team perfectly illustrates the spirit of the IINS. Indeed, every members brings a different expertise."

Can you tell us about your research?

"My research has two goals. The first one is to understand how neurons form connections (or synapses) between themselves. The second is to identify the mechanisms by which they modify those connections, either by strengthening or weakening them, to adapt the brain to its environment. These objectives are hampered by the fact that each single neuron harbours a very large number of synapses (10,000 on average) displaying high molecular and functional diversity […]. In the past years, I have been interested in the role of a cell adhesion protein called ‘neuroligin’, whose function is to connect neurons to each other. On the other hand, some mutations in the ‘neuroligin’ genes are associated with autism. In the team, we have shown that the phosphorylation of this protein plays an important role in the differentiation of excitatory synapses but also in long-term synaptic plasticity, the subcellular substrate for learning and memory.”

You have just been awarded the CNRS Bronze Medal 2023. What does this award mean to you?

"To quote the CNRS, this medal ‘rewards the first achievements of researchers who are specialists in their field’. I am beyond honoured to receive this award. In my eyes, it represents: ‘an incentive from the CNRS to continue my research.’ Although this medal is awarded individually, it rewards work in which many people have participated. I thus owe it to my mentors and colleagues I have met and worked with throughout my career, particularly at IINS and within my team."

An advice for young researchers?

"What I wish for the youngest is to find a stimulating and caring laboratory where they can grow professionally and personally. My advice? Find a question that you are passionate about and never lose sight of it. Question yourself, change your point of view, accept failure and contradiction but also trust yourself. Finally, share your research with your colleagues, friends and family: the greatest ideas rarely pop up from a single brain!"

Read the portrait of Mario Carta in English and French

Mario Carta is a native of Sardegna, Italy. He is a neurobiologist with a long-standing interest in synaptic transmission and plasticity in cortical circuits. Recently, he has been focus his research to the study of how cortical circuits encode sensory information. Thus, together with Mikkel Verstergard a postdoc from the laboratory of James Poulet (MDC, Berlin), they published a study in Nature which reports the discovery of a ‘thermal cortex’ located in a posterior region of the insular cortex. This cortical region is involved in the perception of warm and cool.

You recently published an article in Nature. Can you tell us more about it?
"The cortex receive and compute information from the external world to guide our behaviour. Where and how thermal stimuli are processed in the cortex was not known. Together with Mikkel Verstergard, we wanted to understand how non-painful temperatures are encoded at the single cell level in the mammalian cortex. Therefore, we have developed a preparation to optically access the mouse insular cortex. For this purpose, we used large-scale imaging approaches such as wide-field and two-photon calcium imaging in awake behaving mice to record neuronal activity. Finally, in order to confirm the role of the insular cortex in temperature perception, we performed optogenetic manipulations. Thus, our study demonstrated that cooling and warming are coded differently in the mammalian cortex. This highlight the complexity of temperature perception in the brain!"

What is your background?
"I started by studying biology at the University of Cagliari in Italy. Then I obtained the equivalent of a master’s degree in Valenzuela’s laboratory in Albuquerque, USA. Finally, I returned to Italy and obtained a PhD in neuroscience at the
University of Cagliari. [...] Throughout my career, I have a strong background in slice electrophysiology and I have recently shifted my attention to the investigation of neuronal circuits in behaving animals."

Why did you choose neuroscience?
"During my university studies, neuroscience was the subject that interested and stimulated me the most. More specifically, it was by observing a patch clamp electrophysiological recording of a neuron triggering bursts of action potentials that I decided to go into neuroscience."

Why IINS?
"In 2007, I went to Bordeaux for the first time to participate in the "Escube" summer school organised by Christophe Mulle. It was a very enriching experience with quality science and an active scientific community! The following year, I decided to join Christophe’s team as a postdoctoral researcher. Then, in 2013, I obtained a research position at the CNRS. And, from 2017 to 2022, I did a mission and then a secondment in James Poulet’s laboratory. There I studied how in vivo cortical circuits encode sensory information and control behaviour. In 2022, I finally returned to Bordeaux to co-lead the "Synapses and neural circuits" team alongside Christophe. This was a great opportunity for me. Indeed, it allowed me to gain autonomy and to develop my own research. Moreover, this co-direction allowed me to benefit from the collaboration of an experienced and motivated scientist like Christophe."

Tell us about your research
"Currently, I am focusing to studying the cellular mechanisms and circuits underlying taste processing. So, by studying how cortical neurons respond to taste stimuli, I want to understand how the brain processes and integrates sensory information to generate appropriate behavioural responses. This research could have implications for understanding the neural basis of eating behaviour and related disorders."

Any advice for young researchers?
"First of all, choose and develop a research project that you are passionate about and that makes you happy! This will help you stay motivated and dynamic throughout your (long and sometimes difficult) research. Also, find a laboratory with a healthy and positive environment where you can develop personally and professionally."

The cellular coding of temperature in the mammalian cortex, Nature - February 2023

The cellular coding of temperature in the mammalian cortex.

M. Vestergaard, M. Carta, G. Güney & J. F. A. Poulet - Nature. 2023 Feb 8. doi: 10.1038/s41586-023-05705-5. Online ahead of print.

Warm, cool, these sensations are an integral part of our daily lives. Our ability to detect the temperature of the objects is essential to living. For almost a century, scientists have been trying to determine where in the brain the ability to detect temperatures is located. A study published in Nature reports the discovery of a 'thermal cortex' located in a posterior region of the insular cortex. This cortex can detect cool or warm temperatures.

When our body is in motion, our brain processes the information from our sensory organs. This processing then builds a conscious perception of the world. Much of this process takes place in the outer, folded layer of the brain, called the cortex. The cortex has a major role! It is the house of high brain functions, such as voluntary movement and consciousness.

The scientists started from a previous observation: neurons in the primary somatosensory cortex are active when the skin comes into contact with cool temperatures. They therefore expected that warm temperatures would also be encoded in this region. A test was therefore carried out on mice. To do this, they exposed the front paws of the mice to slight changes in temperature. They then used imaging techniques to find out which part of the brain reacted to these temperature changes. To their surprise, the scientists found that the primary somatosensory cortex did not respond to warming, but on closer inspection, the posterior insular cortex instead responded not only to cooling but also to warming. Using a two-photon microscope, the response of individual neurons in the posterior insular cortex was studied. The scientists discovered that there are cool-specific neurons, warm-specific neurons and neurons that respond to both warm and cool. It should be noted that 'warm' and 'cool' neurons react in very different ways. Indeed, "warm" neurons are sensitive to absolute temperature, while "cool" neurons are activated following a variation in temperature. In addition, the responses of the "cool" neurons are faster than the responses of the "warm" neurons. This indicates that there are potentially separate pathways for the perception of cool and warmth.

To prove conclusively that the insular cortex is involved in temperature perception, the scientists trained mice to respond to cool or warm temperatures. Using optogenetics they were able to temporarily deactivate the posterior insular cortex while delivering a thermal stimulus. In the end, the mice did not feel the thermal stimulus. However, when the scientists stopped deactivating the posterior insular cortex, they felt the stimulus again.

This discovery and the possibility of optically accessing the cortical representation of sensory processing in the insula opens up new avenues of research. First, to study the neural mechanisms of thermal perception, but also to extend similar research to other sensory systems represented in adjacent parts of the insular cortex (in particular the gustatory and visceral systems).

They speak about it too: INSB; CNRS; Bordeaux Neurocampus

Read the portrait of Mario Carta

Contact:

• Mario Carta, chercheur CNRS, mario.carta@u-bordeaux.fr
• James Poulet, professor and group leader, james.poulet@mdc-berlin.de

The Sibarita team "Quantitative Imaging of the Cell" is seeking an engineer to develop light-sheet microscopy for neurosciences applications.

Project description
Light Sheet Fluorescence Microscopy technics (LSFM) have proven to be extremely efficient for 3D imaging of biological samples at various spatial and temporal scales with minimal photo-damaging effects. Several solutions have been developed in the field of neuroscience to image samples ranging from fixed whole brains, to single dissociated neurons growing on a coverslip. In this regard, the Interdisciplinary Institute for Neuroscience (IINS) and the Bordeaux Imaging Center (BIC) are equipped with 3 complementary LSFM techniques: (1) an ultramicroscope for whole brain imging; (2) a Lattice
Light Sheet Microscope (LLSM) to image the first layers of brain slices at high spatial resolution; (3) a home-made single objective selective plane illumination microscope (soSPIM) dedicated to 3D cell cultures and in-depth single-molecule localization microscopy (SMLM).
We aim to complete our catalog by implementing a solution based on the Oblique Plane Microscopy (OPM) architecture, which will be dedicated to fast neuronal samples imaging, ie. brain slices, equipped with local photo-manipulation and possibly other recording modalities.

Missions
The candidate missions will be to:

• develop a custom OPM to address specific neurobiological questions
• participate to the improvement of existing light-sheet microscopes in close collaboration with developers and neuroscientists.

Candidate profile
We seek a motivated, enthusiastic and independent candidate, with an interest in neuroscience and a strong expertise in optics and fluorescence microscopy. Complementary skills in programming and sample preparation are appreciated. The candidate will work in an English-speaking environment, in close interactions with the neuroscientists' team of the Bordeaux's Neurocampus.

Contract
A 3 years research engineer position is available in the framework of the French "Grands Programmes de Recherche" BRAIN awarded to the Bordeaux Neurocampus.
Applicants should send a CV, a motivation letter and contact details for at least two referees to:
jean-baptiste.sibarita@u-bordeaux.fr; remi.galland@u-bordeaux.fr; mathieu.ducros@u-bordeaux.fr

The complete offer

Levet, F., Sibarita, JB

Nat Methods. 2023-03-06

https://doi.org/10.1038/s41592-023-01811-4

Point Cloud Analyst (PoCA) is a powerful open-source software platform dedicated to the visualization and analysis of 2D and 3D point-cloud data. PoCA allows manipulating large datasets, and integrates a plugin architecture, a native batch analysis engine and a Python code interpreter, facilitating both the analysis of data and the integration of new methods.

https://rdcu.be/c6PcJ

PoCA is packaged as a one-click installer for the Windows operating system. The source code is available on GitHub (https://github.com/flevet/PoCA) under a LGPL v3 license. We provide a cmake script to facilitate its building inside other operating systems. The documentation is available at https://poca-smlm.github.io/.

To know more:

• https://github.com/flevet/PoCA
• https://poca-smlm.github.io/

The call is now open and candidates should send their applications to master.applications.light-st@u-bordeaux.fr

The master track “Biophotonics and Neurotechnology” is part of the Light Sciences and Technologies Graduate Program at the University of Bordeaux (EUR or Ecole Universitaire de Recherche and the ‘Mention: Ingénierie de la santé’). This one offers a multidisciplinary training program on advanced microscopy and photonics tools to address complex biological problems in the life sciences, in particular neuroscience and cancer biology.

For who ? Biology, physics, chemistry, engineering undergraduate students, bio-techno-philes of all stripes.

The academic program is composed of:

• basic and specialised lecture and practicum courses,
• internships in active research laboratories and core facilities equipped with state-of-the-arts technology and microscopes,
• supporting infrastructure needed for modern research. 

The courses and practicals are run by leading research faculty and staff, who take pride and interest in teaching and forming the next generation of biophotonics researchers and engineers. The program is run in English and the students study and work in the international, collaborative and diverse research community of Bordeaux Neurocampus.

Key points

• Multidisciplinary training in biophotonics, its technology and application
• An identified area of research excellence at the University of Bordeaux 
• Taught by strong research faculty (including several ERC laureates)
• Financial support offered, M1 and M2 internships are paid + possibility for merit-based fellowships (750€ / month) 
• Career perspectives in academic research (e.g. doctoral school) and private industry, as technology and application specialist, in R&D, sales and service sectors

Moreover, the program offers financial support to all enrolled students (in the form of merit-based “excellence fellowships” and paid internships) and a variety of career opportunities (workshops, summer schools and research stays in France and abroad).

For candidate: master.applications.light-st@u-bordeaux.fr 

More information

• https://formations.u-bordeaux.fr/#/details-formation?type=parcours-type&id=1635
• https://light-st.u-bordeaux.fr/ 
• Light Sciences and Technologies Graduate Program

Contact: Valentin Nägerl, team leader IINS and University professor - Researcher at the Université de Bordeaux

Daniel J. Nieves, Jeremy A. Pike, Florian Levet, David J. Williamson, Mohammed Baragilly, Sandra Oloketuyi, Ario de Marco, Juliette Griffie, Daniel Sage, Edward A. K. Cohen, Jean-Baptiste Sibarita, Mike Heilemann, Dylan M. Owen

Nat Methods. 2023-02-01; 20(2): 259-267

DOI: 10.1038/s41592-022-01750-6

Single-molecule localization microscopy (SMLM) generates data in the form of coordinates of localized fluorophores. Cluster analysis is an attractive route for extracting biologically meaningful information from such data and has been widely applied. Despite a range of cluster analysis algorithms, there exists no consensus framework for the evaluation of their performance. Here, we use a systematic approach based on two metrics to score the success of clustering algorithms in simulated conditions mimicking experimental data. We demonstrate the framework using seven diverse analysis algorithms: DBSCAN, ToMATo, KDE, FOCAL, CAML, ClusterViSu and SR-Tesseler. Given that the best performer depended on the underlying distribution of localizations, we demonstrate an analysis pipeline based on statistical similarity measures that enables the selection of the most appropriate algorithm, and the optimized analysis parameters for real SMLM data. We propose that these standard simulated conditions, metrics and analysis pipeline become the basis for future analysis algorithm development and evaluation.

The point of view of Jean-Baptiste Sibarita and Florian Levet (co-authors)

This work by Nieves et al. proposes metrics to evaluate the performances of clustering methods dedicated to single molecule localization microscopy (SMLM) data. It includes the methods and several reference simulation datasets to assess the performances of existing and future approaches. This is a consortium paper that regroups word wide recognized experts in the field of SMLM. Amongst them, Florian Levet and Jean-Baptiste Sibarita from the Quantitative imaging of the Cell team (IINS) & Bordeaux Imaging Center, contributed to this work as developers of SR-Tesseler and Coloc-Tesseler software and the corresponding methods published in (Levet et al, Nature Methods 2015) and (Levet et al, Nature Comm, 2019).

La Societe des Neurosciences is a non-profit scientific association, governed by the law of 1901.
 Its aim is to promote the development of research in all areas of neuroscience.
 The association brings together scientists and physicians from all over the world whose research and work are focused on the study of the brain and the nervous system.

Every year, la Societe des Neurosciences selects the most outstanding publications in the field of neuroscience. All members of la Societe des Neurosciences are invited to submit articles they have written or read. In 2022, among the 20 selected highlights, there are two highlights where IINS is mentioned.

1. Les synapses pivot a dopamine dans le striatum : un nouveau point nevralgique pour la neuromodulation par la dopamine ?

Vincent Paget-Blanc, Marlene E Pfeffer, Marie Pronot, Paul Lapios, Maria-Florencia Angelo, Roman Walle, Fabrice P Cordelieres, Florian Levet, Stéphane Claverol, Sabrina Lacomme, Melina Petrel, Christelle Martin, Vincent Pitard, Veronique De Smedt Peyrusse, Thomas Biederer, David Perrais, Pierre Trifilieff, Etienne Herzog

Nature Communications. 2022 Jun 3;13(1):3102. 10.1038/s41467-022-30776-9.

2. Une nouvelle boite a outils pour explorer la dynamique des recepteurs dans le cerveau

Angela Getz, Mathieu Ducros, Christel Breillat, Aurelie Lampin-Saint-Amaux, Sophie Daburon, Urielle François, Agata Nowacka, Monica Fernandez Monreal, Eric Hosy, Frederic Lanore, Hanna Zieger, Mathieu Sainlos, Yann Humeau, Daniel Choquet

Science Advances. 2022 Jul 29; 8(30):eabm5298. 10.1126/sciadv.abm5298

Learn more about our research team

Two laureates of the FSER at IINS: Lisa Roux and Jonathan Elegheert

Created on the initiative of a group of scientists wishing to have fundamental research recognised, the Cercle FSER is an association under the French law of 1901. It brings together more than 70 scientists who are committed to fostering the dialogue of science with and for society. To this end, its actions are organised along two main lines: (1) to promote research, its approaches and its challenges to young people, (2) to encourage the involvement of research staff in dialogue with the general public. In 2021, 35,000 people benefited from its actions!

Each year, the Cercle FSER supports young researchers who excel in the field of biomedical research. The candidates are nominated by scientific personalities, former laureates or the CNRS and INSERM. Then, each candidate is selected by a jury on the basis of the quality of his or her past and present scientific research, but also on the basis of his or her performance in the interview.

Thus, Jonathan Elegheert, CNRS scientist (charge de recherches), is one of four laureates of 2022 Cercle FSER! In particular, he obtained the FSER prize, which aims to help young researchers during the first years of their laboratory's creation. This grant enabled Jonathan Elegheert and his team to co-finance a new machine to study protein-protein interactions.

In 2021, Lisa Roux, CNRS research director, was laureate. Like any laureate, the Cercle FSER has enabled her to organise meetings at the Fondation des Treilles! Moreover, as a winner of the Cercle FSER, her objective for 2023 is to participate in the Déclics operation (scientific mediation action with high school students).

One per year, the Cercle FSER organises meetings so that researchers from all disciplines can meet. These exchanges allow them to come up with new and original ideas! The winter meeting took place from 24 to 27 January in Alpe d'Huez. During this meeting, all participants were invited to make a scientific presentation. Thus, Jonathan Elegheert and Lisa Roux intoduced the field of neuroscience! Both presented their research topic: "Structural biology and engineering of neuronal proteins" for Jonathan Elegheert and "Olfaction and Memory" for Lisa Roux.

Would you like to know more? Nolwenn Cloarec, communication officer: nolwenn.cloarec@u-bordeaux.fr

Le Prix Desmarest of the Pierre Deniker Foundation, aims to fund basic research projects in the field of Alzheimer's disease and neurodegenerative diseases, with a total endowment of €100,000. The Pierre Deniker Foundation supports mental health research programs, and raises public awareness of mental disorders.

For this third edition, the Prix Desmarest was awarded to Christophe Mulle, CNRS research director. The project, which will be co-headed by Thierry Amedee, aims to investigate the morpho-functional relationships between microglia and synapses near amyloid plaques in an animal model of Alzheimer's disease. Christophe Mulle was awarded the prize on January 20th at the Encephale Congress (Paris) by Annick Desmarest and by Chantal Henry, scientific director of the Pierre Deniker Foundation.

Learn more about: Christophe Mulle and Thierry Amedee

Do you want to know more? Nolwenn Cloarec, communication officer: nolwenn.cloarec@u-bordeaux.fr

Academie nationale des sciences, belles lettres et arts de Bordeaux aims to help develop the ideas, work and research of Academicians. Each year, it rewards in particular personalities for their work or their research or for all of their work in the field of science, literature or the arts.

Thus, in 2022, it was Daniel Choquet, CNRS research director, who was awarded "le grand prix 2022 de l’Academie nationale des sciences, belles lettres et arts de Bordeaux"! Indeed, he achieved this distinction thanks to his main scientific achievement: the discovery that neurotransmitter receptors are in constant motion in the neuronal membrane and that the regulation of this traffic profoundly regulates synaptic transmission. Daniel Choquet will receive his award on March 28 from Pierre Hurmic, Mayor of Bordeaux.

Learn more about: Le grand prix 2022 de l’Academie nationale des sciences, belles lettres et arts de Bordeaux

They talk about it too (articles in French): INSB and Bordeaux Neurocampus

Do you want to know more? Nolwenn Cloarec, communication officer: nolwenn.cloarec@u-bordeaux.fr

Adapting and staying stable: how neurons modify their connections without compromising their functional integrity

A study conducted under the direction of Mathieu Letellier at the IINS, in the team of Olivier Thoumine and in collaboration with Alexandre Favereaux, reveals a molecular mechanism for homeostatic plasticity in which individual neuronal connections, the “synapses”, compensate for prolonged decrease in neuronal activity by increasing the number of glutamate receptors. This study is published in the EMBO Journal.

Article
miR ‐124‐dependent tagging of synapses by synaptopodin enables input‐specific homeostatic plasticity.
Sandra Dubes, Anaïs Soula, Sébastien Benquet, Béatrice Tessier, Christel Poujol, Alexandre Favereaux, Olivier Thoumine, Mathieu Letellier
The EMBO Journal. 2022-07-25 - 10.15252/embj.2021109012

Highlight
Synaptic tagging: homeostatic plasticity goes Hebbian
Colameo D, Schratt G. EMBO J. 2022 Sep 13:e112383. doi: 10.15252/embj.2022112383. Online ahead of print. PMID: 36097740

Contact
Mathieu Letellier, IINS CNRS researcher

The CNRS Collective Cristal distinguishes teams of women and men, research support staff, who have carried out projects whose technical mastery, collective dimension, applications, innovation and influence are particularly remarkable. This distinction is awarded in two categories: “direct research support” and “research support”.

Congratulations to the Bordeaux Imaging Center (BIC) winner of this distinction!

+ Cf. CNRS website in French here

Neurons are highly polarized cells that face the fundamental challenge of compartmentalizing a vast and diverse repertoire of proteins in order to function properly. The axon initial segment (AIS) is a specialized domain that separates a neuron's morphologically, biochemically and functionally distinct axon and dendrite compartments. How the AIS maintains polarity between these compartments is not fully understood. Here we find that in Caenorhabditis elegans, mouse, rat and human neurons, dendritically and axonally polarized transmembrane proteins are recognized by endocytic machinery in the AIS, robustly endocytosed and targeted to late endosomes for degradation. Forcing receptor interaction with the AIS master organizer, ankyrinG, antagonizes receptor endocytosis in the AIS, causes receptor accumulation in the AIS, and leads to polarity deficits with subsequent morphological and behavioural defects. Therefore, endocytic removal of polarized receptors that diffuse into the AIS serves as a membrane-clearance mechanism that is likely to work in conjunction with the known AIS diffusion-barrier mechanism to maintain neuronal polarity on the plasma membrane. Our results reveal a conserved endocytic clearance mechanism in the AIS to maintain neuronal polarity by reinforcing axonal and dendritic compartment membrane boundaries.
 

Winner of an ERC starting grant in 2016 with the NEUROGOAL project, Frédéric Gambino has just been awarded an ERC consolidator with the MOTORHEAD project.
Congratulations!

Contact: Frédéric Gambino

- See the Bordeaux Neurocampus website here (English)
- See the CNRS INSB website here (French)

Current imaging approaches limit the ability to perform multi-scale characterization of three-dimensional (3D) organotypic cultures (organoids) in large numbers. Here, we present an automated multi-scale 3D imaging platform synergizing high-density organoid cultures with rapid and live 3D single-objective light-sheet imaging. It is composed of disposable microfabricated organoid culture chips, termed JeWells, with embedded optical components and a laser beam-steering unit coupled to a commercial inverted microscope. It permits streamlining organoid culture and high-content 3D imaging on a single user-friendly instrument with minimal manipulations and a throughput of 300 organoids per hour. We demonstrate that the large number of 3D stacks that can be collected via our platform allows training deep learning-based algorithms to quantify morphogenetic organizations of organoids at multi-scales, ranging from the subcellular scale to the whole organoid level. We validated the versatility and robustness of our approach on intestine, hepatic, neuroectoderm organoids and oncospheres.

Authors: Anne Beghin, Gianluca Grenci, Geetika Sahni, Su Guo, Harini Rajendiran, Tom Delaire, Saburnisha Binte Mohamad Raffi, Damien Blanc, Richard de Mets, Hui Ting Ong, Xareni Galindo, Anais Monet, Vidhyalakshmi Acharya, Victor Racine, Florian Levet, Remi Galland, Jean-Baptiste Sibarita and Virgile Viasnoff

Cf. Nature Methods - June 2022 here

Contact: Jean-Baptiste Sibarita

A new hot spot for dopamine transmission?

Dopamine Hub Synapses in the striatum: a new hot spot for dopamine transmission?

How is the conversation between neurons organized in the brain? Through 2 recent articles* we describe part of this organization between the dopamine and surrounding neurons at synapses. Synapses are points of contact between neurons, essential for the proper functioning of the brain. In the brain, neurons are of 2 main types. The effector neurons ensure a rapid and local transmission of information, either excitatory or inhibitory, while the modulatory neurons, few in number, affect large regions of the brain over longer periods of time. Modulatory neurons using dopamine are very important for the tuning of motor control, motivation and reward perception.

In our studies, we established the first selective purification of dopaminergic synapses in the striatum that allowed us to identify 2650 proteins, 57 of which were specifically enriched. In contrast, few messenger RNAs (encoding proteins) are selectively detected, suggesting that local translation of proteins is not a major mechanism at the axons of dopaminergic neurons. In addition, we have identified a new structure where dopaminergic synapses physically interact with other classical synapses and affect the composition of the latter. These "Dopamine Hub Synapses" may mediate dopamine neuromodulation on striatal neuronal circuits, fueling the debate between volume and synaptic models of modulatory transmission. Within this new conceptual framework, future research will provide a detailed understanding of the cellular mechanisms by which dopamine modulates voluntary movements or reward-prediction based learning. This is crucial as many pathologies such as Parkinson's disease, addiction and schizophrenia are linked to dopamine dysfunction.

- Contact: Etienne Herzog, Membrane traffic at synapses

+ Cf. the CNRS INSB website here

* January 2022: Hobson, BD., et al. Subcellular and regional localization of mRNA translation in midbrain dopamine neurons. Cell Reports, 38-2, (2022)
https://doi.org/10.1016/j.celrep.2021.110208.

* June 2022: Paget-Blanc, V., Pfeffer, M.E., Pronot, M. et al. A synaptomic analysis reveals dopamine hub synapses in the mouse striatum. Nat Commun 13, 3102 (2022).
https://doi.org/10.1038/s41467-022-30776-9https://doi.org/10.1038/s41467-022-30776-9

None

The Aquitaine delegation of the CNRS joined with the media Curieux to offer original scientific content promoting the European projects of local researchers. Find here the comic strip produced by Laurent Groc, neurobiologist at IINS, illustrating the role of autoimmunity in the emergence of psychotic disorders. See the project: https://www.curieux.live/.../schizophrenie-et-si-cetait.../

* Cf. the Delegation Aquitaine website here

This conference proposes to bring together among the most famous international and French experts on the molecular and cellular basis of synaptic plasticity, with a focus on its relation to memory. It will take place at the Agora of the Haut-Carré (Talence) from September 27^th to 30^th, 2022.

- Find all details about the Program and contacts here
=> Notice the early-bird rate for registration until June 15th.

uniQure to Acquire Corlieve Therapeutics

Corlieve Therapeutics co-funded by Christophe Mulle and Valérie Crépel (Inserm Marseille) acquired by the biotech uniQure. The acquisition of Corlieve Therapeutics by uniQure amounts to 250 million euros, of which the first initial settlement of 46.3 million euros finalizes the transaction.
 

https://www.bordeaux-neurocampus.fr/en/uniqure-to-acquire-corlieve-therapeutics/

• Dynamic interplay between thalamic activity & Cajal-Retzius cells regulates the wiring of cortical layer1

Cortical wiring relies on guidepost cells and activity-dependent processes that are thought to act sequentially. Here, we show that the construction of layer 1 (L1), a main site of top-down integration, is regulated by crosstalk between transient Cajal-Retzius cells (CRc) and spontaneous activity of the thalamus, a main driver of bottom-up information. While activity was known to regulate CRc migration and elimination, we found that prenatal spontaneous thalamic activity and NMDA receptors selectively control CRc early density, without affecting their demise. CRc density, in turn, regulates the distribution of upper layer interneurons and excitatory synapses, thereby drastically impairing the apical dendrite activity of output pyramidal neurons. In contrast, postnatal sensory-evoked activity had a limited impact on L1 and selectively perturbed basal dendrites synaptogenesis. Collectively, our study highlights a remarkable interplay between thalamic activity and CRc in L1 functional wiring, with major implications for our understanding of cortical development.

The CNRS Silver Medal is awarded to researchers for the originality, quality and importance of their work, recognized at national and international level.
Congratulations to Laurent Groc, CNRS research director and team leader at the IINS, one of the 22 laureates distinguished for this year 2022.

Cf. CNRS website here
 

Frontiers in Bioinformatics, section Computational BioImaging - March 2022

Single molecule localization (SML) and tracking (SPT) techniques, such as (spt)PALM, (u/DNA)PAINT and quantum dot tracking, have given unprecedented insight into the nanoscale molecular organization and dynamics in living cells. They allow monitoring individual proteins with millisecond temporal resolution and high spatial resolution (<30 nm) by precisely localizing the point spread function (PSF) of individual emitters and tracking their position over time. While SPT methods have been extended to study the temporal dynamics and co-organization of multiple proteins, conventional experimental setups are restricted in the number of proteins they can probe simultaneously and usually have to tradeoff between the number of colors, the spatio-temporal resolution, and the field of view. Yet, localizing and tracking several proteins simultaneously at high spatial and temporal resolution within large field of views can provide important biological insights. By employing a dual-objective spectral imaging configuration compatible with live cell imaging combined with dedicated computation tools, we demonstrate simultaneous 3D single particle localization and tracking of multiple distinct species over large field of views to be feasible without compromising spatio-temporal resolution. The dispersive element introduced into the second optical path induces a spectrally dependent displacement, which we used to analytically separate up to five different fluorescent species of single emitters based on their emission spectra. We used commercially available microscope bodies aligned one on top of the other, offering biologists with a very ergonomic and flexible instrument covering a broad range of SMLM applications. Finally, we developed a powerful freely available software, called PALMTracer, which allows to quantitatively assess 3D + t + λ SMLM data. We illustrate the capacity of our approach by performing multi-color 3D DNA-PAINT of fixed samples, and demonstrate simultaneous tracking of multiple receptors in live fibroblast and neuron cultures.

Multi-dimensional spectral Single Molecule Localization Microscopy
Authors: Corey Butler, G. Ezequiel Saraceno, Adel Kechkar, Vincent Studer, Julien P. Dupuis, Laurent Groc, Rémi Galland, Jean-Baptiste Sibarita

Front. Bioinform., 04 March 2022 | https://doi.org/10.3389/fbinf.2022.813494

Contacts: Rémi Galland and Jean-Baptiste Sibarita

+ Cf. Bordeaux Neurocampus website here

Valérie Crépel (INSERM) at the University of Aix-Marseille and Christophe Mulle (CNRS) at the Interdisciplinary Institute for Neuroscience at the University of Bordeaux have been awarded the 2022 Prize for Innovation of the Académie des Sciences et Belles Lettres de Bordeaux.

Valérie Crépel and Christophe Mulle are very high-level researchers interested in the physiology and pathology of the hippocampus circuits, a region of the brain located in the temporal lobes, which is the seat of memory and learning.

Their highly innovative research focuses on the therapeutic approach to the treatment of temporal lobe epilepsy. This pathology affects 1.3 million people in Europe and the United States, including 800,000 patients who are resistant to known treatments. Christophe Mulle and Valérie Crépel propose gene therapy as an alternative to surgery and its drawbacks. Their therapeutic proposal is developed within Corlieve Therapeutics: it uses microRNA technology, nucleic acids capable of acting at the level of messenger RNA to selectively reduce aberrant effects in the hippocampus of patients.

Alzheimer's & Dementia, January 2022

In Alzheimer's disease (AD), the distribution of the amyloid precursor protein (APP) and its fragments other than amyloid beta, has not been fully characterized. Here, we investigate the distribution of APP and its fragments in human AD brain samples and in mouse models of AD in reference to its proteases, synaptic proteins, and histopathological features characteristic of the AD brain, by combining an extensive set of histological and analytical tools. We report that the prominent somatic distribution of APP observed in control patients remarkably vanishes in human AD patients to the benefit of dense accumulations of extra-somatic APP, which surround dense-core amyloid plaques enriched in APP-Nter. These features are accentuated in patients with familial forms of the disease. Importantly, APP accumulations are enriched in phosphorylated tau and presynaptic proteins whereas they are depleted of post-synaptic proteins suggesting that the extra-somatic accumulations of APP are of presynaptic origin. Ultrastructural analyses unveil that APP concentrates in autophagosomes and in multivesicular bodies together with presynaptic vesicle proteins. Altogether, alteration of APP distribution and its accumulation together with presynaptic proteins around dense-core amyloid plaques is a key histopathological feature in AD, lending support to the notion that presynaptic failure is a strong physiopathological component of AD.

APP accumulates with presynaptic proteins around amyloid plaques: a role for presynaptic mechanisms in Alzheimer’s disease?
Authors: Tomàs Jordà-Siquier, Melina Petrel, Vladimir Kouskoff, Una Smailovic, Fabrice Cordelières, Susanne Frykman, Ulrike Müller, Christophe Mulle, Gaël Barthet

Alzheimer's & Dementia, The Journal of the Alzheimer's Association - 25 January 2022 DOI: 10.1002/alz.12546

Contacts: Gaël Barthet and Christophe Mulle

+ Cf. CNRS Press release in French here
+ Cf Bordeaux Neurocampus website here

Nature Communications, November 2021

Progress in biological imaging is intrinsically linked to advances in labeling methods. The explosion in the development of high-resolution and super-resolution imaging calls for new approaches to label targets with small probes. These should allow to faithfully report the localization of the target within the imaging resolution – typically nowadays a few nanometers - and allow access to any epitope of the target, in the native cellular and tissue environment. We report here the development of a complete labeling and imaging pipeline using genetic code expansion and non-canonical amino acids in neurons that allows to fluorescently label masked epitopes in target transmembrane proteins in live neurons, both in dissociated culture and organotypic brain slices. This allows us to image the differential localization of two AMPA receptor (AMPAR) auxiliary subunits of the transmembrane AMPAR regulatory protein family in complex with their partner with a variety of methods including widefield, confocal, and dSTORM super-resolution microscopy.

Authors: Diogo Bessa-Neto & Gerti Beliu, Alexander Kuhlemann, Valeria Pecoraro, Sören Doose, Natacha Retailleau, Nicolas Chevrier, David Perrais, Markus Sauer & Daniel Choquet

Bioorthogonal labeling of transmembrane proteins with non-canonical amino acids unveils masked epitopes in live neurons.
Nature Communications (November 2021) DOI: 10.1038/s41467-021-27025-w

Contact: Daniel Choquet

+ Cf. INSB website (French) here
+ Cf. the press release on the University of Würzburg website here

Nature Cell Biology, November 2021

Actin filaments generate mechanical forces that drive membrane movements during trafficking, endocytosis and cell migration. Reciprocally, adaptations of actin networks to forces regulate their assembly and architecture. Yet, a demonstration of forces acting on actin regulators at actin assembly sites in cells is missing. Here we show that local forces arising from actin filament elongation mechanically control WAVE regulatory complex (WRC) dynamics and function, that is, Arp2/3 complex activation in the lamellipodium. Single-protein tracking revealed WRC lateral movements along the lamellipodium tip, driven by elongation of actin filaments and correlating with WRC turnover. The use of optical tweezers to mechanically manipulate functional WRC showed that piconewton forces, as generated by single-filament elongation, dissociated WRC from the lamellipodium tip. WRC activation correlated with its trapping, dwell time and the binding strength at the lamellipodium tip. WRC crosslinking, hindering its mechanical dissociation, increased WRC dwell time and Arp2/3-dependent membrane protrusion. Thus, forces generated by individual actin filaments on their regulators can mechanically tune their turnover and hence activity during cell migration.

Authors: Amine Mehidi, Frieda Kage, Zeynep Karatas, Maureen Cercy, Matthias Schaks, Anna Polesskaya, Matthieu Sainlos, Alexis Gautreau, Olivier Rossier, Klemens Rottner and Grégory Giannone

Forces generated by lamellipodial actin filament elongation regulate the WAVE complex during cell migration
Nature Cell Biology, 23, pages 1148–1162 (2021). https://www.nature.com/articles/s41556-021-00786-8

*Contact IINS: Grégory Giannone

+ Cf. INSB website (French) here
+ Cf. Bordeaux Neurocampus website here

Synapses, the basic building blocks of neural networks, are both very stable and capable of rapid and long-lasting modifications, a phenomenon known as synaptic plasticity. The modification of a synapse often involves the addition of synaptic receptors (long-term potentiation or LTP) or the removal of part of the synaptic receptors (long-term depression or LTD). This rapid plasticity is possible because synaptic receptors are not immobile in the synapse but travel to intracellular compartments called recycling endosomes (RE). The regulation of RE trafficking has thus become an important topic of study for understanding the mechanisms of synaptic plasticity.

Picture of all contributors of this study. David Perrais and May Bakr stand in front of "The paint pipette", taken by May, which was awarded the best IINS picture prize in 2020.

In this study, we searched for the molecules involved in these phenomena, in particular the proteins responsible for exocytosis called SNAREs. The VAMP2 protein, target of the tetanus toxin (released by the bacterium responsible for tetanus and one of the most deadly in humans), was known to block LTP. However, to our surprise, it only marginally affected RE exocytosis. We therefore searched for other SNARE proteins and found VAMP4 to be responsible for the majority of RE exocytosis, whereas VAMP2 is involved in only a small fraction of exocytosis, but plays a major role in the exocytosis of REs containing AMPA-type postsynaptic receptors (see Figure). Furthermore, VAMP4 deletion also alters the trafficking of AMPA receptors that are in greater quantity at the surface of neurons, increasing synaptic transmission and limiting its plasticity by occlusion.
This work shows the great diversity of membrane trafficking mechanisms in the dendrites of neurons that allows receptors to be delivered when and where they are needed to regulate individual synapses. It was the result of a long-term work, over more than eight years, of many students, engineers and researchers of the IINS.

The startup Corlieve Therapeutics co-founded by Christophe Mulle PI @IINS just sold to UNIQURE for 250 M€

Happy to celebrate the sale of Corlieve Therapeutics for 250 M€, the startup created by Christophe Mulle and Valérie Crépel from their work partly at IINS.

Corlieve Therapeutics is a biotechnology company focused on bringing novel therapeutic options to patients with severe neurological disorders. The lead project is targeting aberrantly expressed kainate receptors in the hippocampus of patients with refractory Temporal Lobe Epilepsy using a gene therapy approach.

More info here

Dates: October 21-22, 2021 on ZOOM. The symposium is funded by the DFG Collaborative Research Center 936 (SFB 936). To know more, follow the link below.

The Schlumberger Foundation for Education and Research selects each year three laureates amongst the best young researchers who are building their team in the field of life sciences. A group leader of IINS, Lisa Roux, is one of the laureates in 2021. She has just received a prize to support the establishment of her team and will join the Cercle FSER in taking action to defend and highlight the value of basic science research.

Congratulations to him!

Molecular motion and tridimensional nanoscale localization of kindlin control integrin activation in focal adhesions

Focal adhesions (FAs) initiate chemical and mechanical signals involved in cell polarity, migration, proliferation and differentiation. Super-resolution microscopy revealed that FAs are organized at the nanoscale into functional layers from the lower plasma membrane to the upper actin cytoskeleton. Yet, how FAs proteins are guided into specific nano-layers to promote interaction with given targets is unknown. Using single protein tracking, super-resolution microscopy and functional assays, we link the molecular behavior and 3D nanoscale localization of kindlin with its function in integrin activation inside FAs. We show that immobilization of integrins in FAs depends on interaction with kindlin. Unlike talin, kindlin displays free diffusion along the plasma membrane outside and inside FAs. We demonstrate that the kindlin Pleckstrin Homology domain promotes membrane diffusion and localization to the membrane-proximal integrin nano-layer, necessary for kindlin enrichment and function in FAs. Using kindlin-deficient cells, we show that kindlin membrane localization and diffusion are crucial for integrin activation, cell spreading and FAs formation. Thus, kindlin uses a different route than talin to reach and activate integrins, providing a possible molecular basis for their complementarity during integrin activation.

The Bordeaux Neuroscience center of excellence

The BRAIN_2030 project (“Bordeaux Region Aquitaine Initiative for the future of Neurosciences”), submitted by Bordeaux Neurocampus within the “GPR - Major Research Program” of the University of Bordeaux, and headed by Daniel Choquet, has just been approved. It is one of the 7 projects selected out of the 15 submitted in June 2020.

A dialogue phase is planned to validate the final budget that will be allocated for the period 2021-2025. Additional funding for an additional period will be granted after an interim evaluation in 2025.

The project starts in September 2021.

+ Find more details on the Université of Bordeaux (UB) and the Bordeaux Neurocampus (BN) websites.

The extracellular space plays a central role in brain physiology

Super‐resolution shadow imaging reveals local remodeling of astrocytic microstructures and brain extracellular space after osmotic challenge

The extracellular space (ECS) plays a central role in brain physiology, shaping the time course and spread of neurochemicals, ions, and nutrients that ensure proper brain homeostasis and neuronal communication. Astrocytes are the most abundant type of glia cell in the brain, whose processes densely infiltrate the brain's parenchyma. As astrocytes are highly sensitive to changes in osmotic pressure, they are capable of exerting a potent physiological influence on the ECS. However, little is known about the spatial distribution and temporal dynamics of the ECS that surrounds astrocytes, owing mostly to a lack of appropriate techniques to visualize the ECS in live brain tissue. Mitigating this technical limitation, we applied the recent SUper‐resolution SHadow Imaging technique (SUSHI) to astrocyte‐labeled organotypic hippocampal brain slices, which allowed us to concurrently image the complex morphology of astrocytes and the ECS with unprecedented spatial resolution in a live experimental setting. Focusing on ring‐like astrocytic microstructures in the spongiform domain, we found them to enclose sizable pools of interstitial fluid and cellular structures like dendritic spines. Upon experimental osmotic challenge, these microstructures remodeled and swelled up at the expense of the pools, effectively increasing the physical interface between astrocytic and cellular structures. Our study reveals novel facets of the dynamic microanatomical relationships between astrocytes, neuropil, and the ECS in living brain tissue, which could be of functional relevance for neuron–glia communication in a variety of (patho)physiological settings, for example, LTP induction, epileptic seizures or acute ischemic stroke, where osmotic disturbances are known to occur.

The EU Research and Innovation Magazine

On the role of social scents. Article by Alex Whiting.

Interviews (in French) on olfactory perception and the link between olfaction and memory.

Chaque année, les étudiant·es du master Médiation des sciences de Bordeaux et l’association Dealers de Sciences organisent une semaine de culture scientifique et technique. Pour sa 5ème édition, la thématique choisie est « L’Enquête des Sens ». Lisa Roux et Pascal Ravassard ont répondu aux questions de leur interviewers sur la perception olfactive (https://www.lenquetedessens.dealersdescience.com/index.php/2020/10/03/les-serrures-de-lodorat/) et le lien entre mémoire et odorat (https://www.lenquetedessens.dealersdescience.com/index.php/2020/11/08/les-echos-de-la-memoire/).

Semaine du cerveau 2021

The 23^rd Brain Week takes place from March 15 to 22, 2021.

Several online events are proposed by the Neuroscience Bordeaux community.
Find the events organized locally on the websites of Bordeaux Neurocampus and Société des neurosciences and visit the scientific image exhibition created by IINS. Find the best pictures from IINS members with their legends.

Follow this link : https://neuro-extramuros.u-bordeaux.fr/CERVEAU2021/

Nature Neuroscience Review - Advanced imaging and labelling methods to decipher brain cell organization and function

We review the latest developments for labelling and functionalizing proteins with small localization and functionalized reporters. We present how these molecular tools are combined with the development of a wide variety of imaging methods that break either the diffraction barrier or the tissue penetration depth limits. We put these developments in perspective to emphasize how they will enable step changes in our understanding of the brain.

An increase in dendritic plateau potentials is associated with experience-dependent cortical map reorganization

New members join the team for 2021

We are pleased to welcome several new members:

Sarka Jelinkova - Post Doctoral Fellow - Expert in Stem cell biology and molecular biology - Ph.D U Brno - Czech Republic

Nathan Hoareau - Master 2 rotation student - Ecole Supérieure de Chimie Organique et Minerale

Juan Manuel Defauce Garcia - Master 1 NeuroBIM rotation student - Université de Bordeaux

Khadija Inam - Master 1 NeuroBIM rotation student - Université de Bordeaux

Fantine Morinière - Technician degree rotation student - BTS Biotechnologies - Lycée Saint-Louis - Bordeaux

Welcome to all of them!

Malezieux, Kees, and Mulle, Cell Reports 2020

Wakefulness is comprised of distinct brain states correlated with different behaviors and stages of memory.  It is hypothesized that memory encoding and recall are more prominent during active behaviors, while memory consolidation is more prominent during rest.  The hippocampal region of the brain is involved in all these stages of memory during their respective brain states. For this brain circuit to perform these different computations at different times, it has been hypothesized that the membrane potential of individual neurons must change in a brain state-dependent manner.  We sought to test this hypothesis by recording membrane potential from individual CA3 hippocampal pyramidal cells in awake mice during active and restful behaviors.  When animals are actively moving, the hippocampal local field potential displays a 4-12 Hz oscillation known as theta. We found that, consistent with the hypothesis, CA3 pyramidal cells underwent consistent changes in membrane potential when theta was present in the local field potential.  Specifically, these cells hyperpolarized, decreased firing, and had low membrane potential variance, all of which are consistent with increased inhibition. This sustained, coherent suppression of CA3 pyramidal cells during theta likely changes the circuit dynamics within the hippocampus, contributing to a functional switch that might underlie the ability of the hippocampus to participate in memory encoding during theta.

- Cell Reports 2020 - doi: 10.1016/j.celrep.2020.107868

- Authors and contacts: Meryl Malezieux, Ashley L Kees and Christophe Mulle 

+ Cf Bordeaux Neurocampus website here

The new Studer’s IINS team and the Alvéole company launch the CNRS joint laboratory "Cell Organ-izers". See the video.

Faced with the same challenges for their academic research work or their clients needs, the IINS group led by Vincent Studer “Organ-izing the cell” and Alvéole have decided to create a common laboratory "Cell Organ_izers". It will aim at establishing a tight research partnership, likely to have a leverage effect in terms of both scientific production and innovation. The general theme of research of the JRL will be the development of  scale up tools and methods to craft standardized human in vitro models for biology with the general goal of reconciliating the simplicity of in vitro models with complex properties encountered in vivo. We will focus our investigations on tools, methods and principles in straight line with Alveole’s product line, patent portfolio and target market. The results that we have obtained together within our previous collaboration contracts will be the starting bricks of the program.

Contact: vincent.studer at u-bordeaux.fr
+ See the Bordeaux Neurocampus website here
 

Together with my Bordeaux colleagues (E. Bezard, L. Cognet and L. Groc), I am a proud recipient of an ERC Synergy grant from the EU, which supports high-risk/high gain frontier research in Europe. This is a tremendous recognition of our work, which will give us resources and wings to conduct some cool and ground-breaking research in the years to come! I am extremely grateful to all the members of my team and collaborators who have contributed to this success over the years and made it possible.

A simulator of single molecule dynamics for fluorescence live-cell and super-resolution imaging of membrane proteins

We introduce fast, robust, and user-friendly software called FluoSim that allows for real time simulation of membrane protein dynamics in live-cell imaging and super-resolution modalities. We also show that FluoSim can be used to produce large virtual data sets for training deep neural networks for image reconstruction. This software should thus be of great interest to a wide community specialized in imaging methods applied to cell biology and neuroscience, with the common aim to better understand membrane dynamics and organization in cells. FluoSim is freely available on the website of the publisher Scientific Reports.

FluoSim: simulator of single molecule dynamics for fluorescence live-cell and super-resolution imaging of membrane proteins
- Authors: Lagardère M, Chamma I, Bouilhol E, Nikolski M, Thoumine
- Scientific Reports 10, 19954 (2020). https://doi.org/10.1038/s41598-020-75814-y

+ See the movie here

Movie Legend:
Simulation of a Fluorescence Recovery After Photobleaching (FRAP) experiment.
The movie generated with FluoSim shows the distribution of surface receptors in a dendritic segment, with specific accumulation in post-synaptic areas (red color).
Receptors are photobleached at t = 5 sec in two specific synapses. Note the fluorescence recovery over time (total 60 sec), due to receptor diffusion and turnover.

The ENSEMBLE project aims at underpinning the molecular mechanisms of physiological and pathological brain function.

Congratulations to our ERC synergy 2020 awardees L. Groc, E. Bézard, V. Nägerl and L. Cognet!

We are happy and proud of this selection that will further expand our knowledge of the properties and function of the Brain extracellular space.

The teams of Laurent Groc (Research Director CNRS; Interdisciplinary Institute for Neuroscience), Erwan Bézard (Research Director Inserm; Institute of Neurodegenerative Disorders), Laurent Cognet (Research Director CNRS; Laboratoire photonique numérique et nanosciences) and Valentin Nägerl (Professor at University of Bordeaux; Interdisciplinary Institute for Neuroscience)  have been awarded the ERC Synergy Award 2020. The ENSEMBLE project aims at underpinning the molecular mechanisms of physiological and pathological brain function. This ambitious and innovative endeavor is based on their ability to develop new approaches in high-resolution microscopy at the service of a new conceptual framework in brain cell communication.

This project has roots in the international leadership of the Bordeaux community in the fields of microscopy, nanophotonics, fundamental and translational neuroscience. The opportunity that is offered to these 4 investigators to break a frontier knowledge was permitted by the continuous support of local institutional actors. The installation of Prof. Valentin Nägerl’s laboratory in 2009 with a "Chaire Accueil" from the Regional Council of Nouvelle-Aquitaine, the support of LabEx BRAIN, the Laphia Cluster and the IdEx of the University of Bordeaux provided the ground to build elementary blocks necessary for the challenging adventure of the ERC Synergy project (10 million euros, 6 years).

+ See the Bordeaux Neurocampus website 

Nature Neuroscience has selected the Naoya Takahashi's last paper 'Active dendritic currents gate descending cortical outputs in perception' for his October 2020 volume cover.

Physiologically relevant cell‐based models require engineered microenvironments

Physiologically relevant cell‐based models require engineered microenvironments which recapitulate the topographical, biochemical, and mechanical properties encountered in vivo. In this context, hydrogels are the materials of choice. Here a light based toolbox is able to craft such microniches out of common place materials. Extensive use of benzophenone photoinitiators and their interaction with oxygen achieves this. First, the oxygen inhibition of radicals is harnessed to photoprint hydrogel topographies. Then the chemical properties of benzophenone are exploited to crosslink and functionalize native hydrogels lacking photosensitive moieties. At last, photoscission is introduced: an oxygen driven, benzophenone‐enabled reaction that photoliquefies Matrigel and other common gels. Using these tools, soft hydrogel templates are tailored for cells to grow or self organize into standardized structures. The described workflow emerges as an effective microniche manufacturing toolset for 3D cell culture.

Authors: Aurélien Pasturel, Pierre‐Olivier Strale, Vincent Studer

- Advanced Healthcare Materials - First published: 02 August 2020 - https://doi.org/10.1002/adhm.202000519
- Contact: Vincent Studer

+ Thumbnail Leg. This spheroidally shaped cell culture of human embryonic kidney cells was templated by a photochemical technique. Vincent Studer and co-workers used photochemistry to controllably create hollow shapes within hydrogel structures. These hollows were then seeded with cells, which grew to fill the empty space. The spheroids were stained using a cell marker and the 3D imaging was accomplished with a bespoke digital micromirror-device-based confocal microscope.

Every year, as part of a partnership, Inserm and the French National Center for Scientific Research (CNRS) launch a call for proposals aimed at enabling young researchers to create and lead a team within an established Inserm or CNRS research center. The teams formed will work to strengthen the research of the host unit by independently developing their own research projects. This program aims to promote mobility and attract young, high-caliber team leaders.

Congratulations to Naoya Takahashi, IINS member, that is in the list of the selected candidates of the ATIP-Avenir - 2020!

Contact: Naoya Takahashi

Extrasynaptic actions of glutamate are limited by high-affinity transporters expressed by perisynaptic astroglial processes (PAPs): this helps maintain point-to-point transmission in excitatory circuits. Memory formation in the brain is associated with synaptic remodeling, but how this affects PAPs and therefore extrasynaptic glutamate actions is poorly understood. Here, we used advanced imaging methods, in situ and in vivo, to find that a classical synaptic memory mechanism, long-term potentiation (LTP), triggers withdrawal of PAPs from potentiated synapses. Optical glutamate sensors combined with patch-clamp and 3D molecular localization reveal that LTP induction thus prompts spatial retreat of astroglial glutamate transporters, boosting glutamate spillover and NMDA-receptor-mediated inter-synaptic cross-talk. The LTP-triggered PAP withdrawal involves NKCC1 transporters and the actin-controlling protein cofilin but does not depend on major Ca2+-dependent cascades in astrocytes. We have therefore uncovered a mechanism by which a memory trace at one synapse could alter signal handling by multiple neighboring connections.

Christian Henneberger et al in Neuron (2020)

This is a rat hippocampal neuron in culture stained with a series of markers

 

 

Cell Reports, Sept. 2020

AMPAR-Dependent Synaptic Plasticity Initiates Cortical Remapping and Adaptive Behaviors during Sensory Experience

Cortical plasticity improves behaviors and helps recover lost functions after injury. However, the underlying synaptic mechanisms remain unclear. In mice, we show that trimming all but one whisker enhances sensory responses from the spared whisker in the barrel cortex and occludes whisker-mediated synaptic potentiation (w-Pot) in vivo. In addition, whisker-dependent behaviors that are initially impaired by single-whisker experience (SWE) rapidly recover when associated cortical regions remap. Cross-linking the surface GluA2 subunit of AMPA receptors (AMPARs) suppresses the expression of w-Pot, presumably by blocking AMPAR surface diffusion, in mice with all whiskers intact, indicating that synaptic potentiation in vivo requires AMPAR trafficking. We use this approach to demonstrate that w-Pot is required for SWE-mediated strengthening of synaptic inputs and initiates the recovery of previously learned skills during the early phases of SWE. Taken together, our data reveal that w-Pot mediates cortical remapping and behavioral improvement upon partial sensory deafferentation.

Authors: Tiago Campelo, Elisabete Augusto, Nicolas Chenouard, Come Camus, Daniel Choquet, Frédéric Gambino

- Cell Reports, Sept. 2020 - DOI:https://doi.org/10.1016/j.celrep.2020.108097
- Contacts: Frédéric Gambino and Daniel Choquet

Distance-dependent regulation of NMDAR nanoscale organization along hippocampal neuron dendrites

Hippocampal pyramidal neurons are characterized by a unique arborization subdivided in segregated dendritic domains receiving distinct excitatory synaptic inputs with specific properties and plasticity rules that shape their respective contributions to synaptic integration and action potential firing. Although the basal regulation and plastic range of proximal and distal synapses are known to be different, the composition and nanoscale organization of key synaptic proteins at these inputs remains largely elusive. Here we used superresolution imaging and single nanoparticle tracking in rat hippocampal neurons to unveil the nanoscale topography of native GluN2A- and GluN2B-NMDA receptors (NMDARs) -which play key roles in the use-dependent adaptation of glutamatergic synapses- along the dendritic arbor. We report significant changes in the nanoscale organization of GluN2B-NMDARs between proximal and distal dendritic segments, whereas the topography of GluN2A-NMDARs remains similar along the dendritic tree. Remarkably, the nanoscale organization of GluN2B-NMDARs at proximal segments depends on their interaction with calcium/calmodulin-dependent protein kinase II (CaMKII), which is not the case at distal segments. Collectively, our data reveal that the nanoscale organization of NMDARs changes along dendritic segments in a subtype-specific manner and is shaped by the interplay with CaMKII at proximal dendritic segments, shedding light on our understanding of the functional diversity of hippocampal glutamatergic synapses.

Authors: Joana S. Ferreira, Julien P. Dupuis, Blanka Kellermayer, Nathan Bénac, Constance Manso, Delphine Bouchet, Florian Levet, Corey Butler, Jean-Baptiste Sibarita, and Laurent Groc

Science, August 2020

A synthetic synaptic organizer protein restores glutamatergic neuronal circuits

The human brain contains trillions of synapses within a vast network of neurons. Synapse remodeling is essential to ensure the efficient reception and integration of external stimuli and to store and retrieve information. Building and remodeling of synapses occurs throughout life under the control of synaptic organizer proteins. Errors in this process can lead to neuropsychiatric or neurological disorders. Suzuki et al. combined structural elements of natural synaptic organizers to develop an artificial version called CPTX, which has different binding properties (see the Perspective by Salinas). CPTX could act as a molecular bridge to reconnect neurons and restore excitatory synaptic function in animal models of cerebellar ataxia, familial Alzheimer’s disease, and spinal cord injury. The findings illustrate how structure-guided approaches can help to repair neuronal circuits.

Authors: Kunimichi Suzuki, Jonathan Elegheert, Inseon Song, Hiroyuki Sasakura, Oleg Senkov, Keiko Matsuda, Wataru Kakegawa, Amber J. Clayton, Veronica T. Chang, Maura Ferrer-Ferrer, Eriko Miura, Rahul Kaushik, Masashi Ikeno, Yuki Morioka, Yuka Takeuchi, Tatsuya Shimada, Shintaro Otsuka, Stoyan Stoyanov, Masahiko Watanabe, Kosei Takeuchi, Alexander Dityatev, A. Radu Aricescu, Michisuke Yuzaki

- Science, 28 Aug 2020: Vol. 369, Issue 6507, eabb4853 - DOI: 10.1126/science.abb4853
- Contact: Jonathan Elegheert

Nature Cell Biology, July 2020

Cell stretching is amplified by active actin remodeling to deform and recruit proteins in mechano-sensitive structures Detection and conversion of mechanical forces into biochemical signals control cell functions during physiological and pathological processes. Mechano-sensing is based on protein deformations and reorganizations, yet the molecular mechanisms are still unclear. Using a cell stretching device compatible with super-resolution microscopy (SRM) and single protein tracking (SPT), we explored the nanoscale deformations and reorganizations of individual proteins inside mechano-sensitive structures. We achieved SRM after live stretching on intermediate filaments, microtubules and integrin adhesions. Simultaneous SPT and stretching showed that while integrins follow the elastic deformation of the substrate, actin filaments and talin also displayed lagged and transient inelastic responses associated with active acto-myosin remodeling and talin deformations. Capturing acute reorganizations of single-molecule during stretching showed that force-dependent vinculin recruitment is delayed and depends on the maturation of integrin adhesions. Thus, cells respond to external forces by amplifying transiently and locally cytoskeleton displacements enabling protein deformation and recruitment in mechano-sensitive structures.

Authors: Sophie Massou*, Filipe Nunes Vicente*, Franziska Wetzel*, Amine Mehidi, Dan Strehle, Cecile Leduc, Raphaël Voituriez, Olivier Rossier, Pierre, Nassoy and Gregory Giannone
* First co-authors

Nature Cell Biology, DOI 10.1038/s41556-020-0548-2.
Contacts IINS: Grégory Giannone and Filipe Nunes Vicente

+ Cf. INSB website (French) here
+ Cf. Bordeaux Neurocampus website here

On the new Aquitaine Delegation website find dedicated pages to the organization of the Delegation, scientific potential, innovation, as well as an agenda and a News section here

Progress in Neurobiology, May 2020

Synaptic loss is the best correlate of cognitive deficits in Alzheimer’s disease (AD). Extensive experimental evidence also indicates alterations of synaptic properties at the early stages of disease progression, before synapse loss and neuronal degeneration. A majority of studies in mouse models of AD have focused on post-synaptic mechanisms, including impairment of long-term plasticity, spine structure and glutamate receptor-mediated transmission. Here we review the literature indicating that the synaptic pathology in AD includes a strong presynaptic component. We describe the evidence indicating presynaptic physiological functions of the major molecular players in AD. These include the amyloid precursor protein (APP) and the two presenilin (PS) paralogs PS1 or PS2, genetically linked to the early-onset form of AD, in addition to tau which accumulates in a pathological form in the AD brain. Three main mechanisms participating in presynaptic functions are highlighted. APP fragments bind to presynaptic receptors (e.g. nAChRs and GABAB receptors), presenilins control Ca2+ homeostasis and Ca2+-sensors, and tau regulates the localization of presynaptic molecules and synaptic vesicles. We then discuss how impairment of these presynaptic physiological functions can explain or forecast the hallmarks of synaptic impairment and associated dysfunction of neuronal circuits in AD. Beyond the physiological roles of the AD-related proteins, studies in AD brains also support preferential presynaptic alteration. This review features presynaptic failure as a strong component of pathological mechanisms in AD.

 Progress in Neurobiology 2020 - doi:10.1016/j.pneurobio.2020.101801
 Authors and contacts: Gaël Barthet and Christophe Mulle

+ Cf Bordeaux Neurocampus website here

Science Advances, July 2020

Human endogenous retroviral protein triggers deficit in glutamate synapse maturation and behaviors associated with psychosis 

Mobile genetic elements, such as human endogenous retroviruses (HERVs), produce proteins that regulate brain cell functions and synaptic transmission and have been implicated in the etiology of neurological and neurodevelopmental psychiatric disorders. However, the mechanisms by which these proteins of retroviral origin alter brain cell communication remain poorly understood. Here, we combined single-molecule tracking, calcium imaging, and behavioral approaches to demonstrate that the envelope protein (Env) of HERV type W, which is normally silenced but expressed in patients with neuropsychiatric conditions, alters the N-methyl-d-aspartate receptor (NMDAR)–mediated synaptic organization and plasticity through glia- and cytokine-dependent changes. Env expression in the developing hippocampus was sufficient to induce behavioral impairments at the adult stage that were prevented by Env neutralization or tuning of NMDAR trafficking. Thus, we show that a HERV gene product alters glutamate synapse maturation and generates behavioral deficits, further supporting the possible etiological interplay between genetic, immune, and synaptic factors in psychosis.

Authors: E.M. Johansson, D. Bouchet, R. Tamouza, P. Ellul, AS. Morr, E. Avignone, R. Germi, M. Leboyer, H. Perron and L. Groc

- Science Advances 17 Jul 2020: Vol. 6, no. 29, eabc0708 - DOI: 10.1126/sciadv.abc0708
- Contacts: Emily M. Johannson and Laurent Groc
+ More details on the Neurocampus website here

Current Opinion in Neurobiology, August 2020

Review on “AMPA receptor nanoscale dynamic organization and synaptic plasticities” in Current Opinion in Neurobiology 2020

The emergence of new imaging techniques and molecular tools has refreshed our understanding of the principles of synaptic transmission and plasticity. Superresolution imaging and biosensors for measuring enzymatic activities in live neurons or neurotransmitter levels in the synaptic cleft are giving us an unprecedented integrated and nanoscale view on synaptic function. Excitatory synapses are now conceptualized as organized in subdomains, enriched with specific scaffolding proteins and glutamate receptors, molecularly organized with respect to the pre-synaptic source of glutamate.

This new vision of basic synaptic transmission changes our understanding of the molecular modifications which sustain synaptic plasticities. Long-term potentiation can no longer be explained simply by an increase in receptor content at the synapse. We review here the latest data on the role of nanoscale and dynamic organization of AMPA type glutamate receptors on synaptic transmission at both basal state and during short and long-term plasticities.

 Current Opinion in Neurobiology - Volume 63, August 2020, Pages 137-145 https://doi.org/10.1016/j.conb.2020.04.003
 Contacts: Daniel Choquet and Eric Hosy

PNAS, June 2020

Nanoscale co-organization and coactivation of AMPAR, NMDAR, and mGluR at excitatory synapses.

The nanoscale co-organization of neurotransmitter receptors facing presynaptic release sites is a fundamental determinant of their coactivation and of synaptic physiology. At excitatory synapses, how endogenous AMPARs, NMDARs, and mGluRs are co-organized inside the synapse and their respective activation during glutamate release are still unclear. Combining single-molecule super resolution microscopy, electrophysiology, and modeling, we determined the average quantity of each glutamate receptor type, their nanoscale organization, and their respective activation. We observed that NMDARs form a unique cluster mainly at the center of the PSD, while AMPARs segregate in clusters surrounding the NMDARs.mGluR5 presents a different organization and is homogenously dispersed at the synaptic surface. From these results, we build a model predicting the synaptic transmission properties of a unitary synapse, allowing better understanding of synaptic physiology.

Authors: Julia Goncalves, Tomas M. Bartol, Côme Camus, Florian Levet, Ana Paula Menegolla,Terrence J. Sejnowski, Jean-Baptiste Sibarita, Michel Vivaudou, Daniel Choquet and Eric Hosy

- Publication in PNAS, June 8, 2020 https://doi.org/10.1073/pnas.1922563117
- Contact: Eric Hosy

Science, June 2020

Linking glutamate receptor movements and synapse function
Regulation of neurotransmitter receptor content at synapses is achieved through a dynamic equilibrium between biogenesis and degradation pathways, receptor stabilization at synaptic sites, and receptor trafficking in and out synapses. In the past 20 years, the movements of receptors to and from synapses have emerged as a series of highly regulated processes that mediate postsynaptic plasticity. Our understanding of the properties and roles of receptor movements has benefited from technological advances in receptor labeling and tracking capacities, as well as from new methods to interfere with their movements. Focusing on two key glutamatergic receptors, we review here our latest understanding of the characteristics of receptor movements and their role in tuning the efficacy of synaptic transmission in health and brain disease.

Authors: Laurent Groc and Daniel Choquet

 Review Science 368, eaay4631, June 2020 - Doi: 10.1126/ science.aay4631
 Contacts: Laurent Groc, Daniel Choquet

+ Cf. PDF version.
+ Cf Bordeaux Neurocampus website here
+ Cf. INSB info-press (in French), here

MemTraS - Membrane traffic at synapses

"MemTraS - Membrane traffic at synapses" is a new team recently born at IINS. The leader, David Perrais, presents the research axis:
Our goal in the team is to study the mechanisms of synapse function. We focus on membrane trafficking events, exocytosis and endocytosis, in normal brain physiology or in the course of disease. Indeed, membrane trafficking is essential in both sides of the synapse. The presynaptic element is filled with synaptic vesicles which fuse at the active zone to release neurotransmitter molecules, one of the defining features of synaptic transmission. After fusion, vesicles are very quickly and efficiently recycled to cope with neuronal activity. At the post-synaptic side, post-synaptic receptors are going through cycles of endocytosis and recycling, which is essential to regulate synaptic transmission and plasticity. We want to analyse how these processes are organized in space and time. Finally, we are not only interested in canonical synapses, such as cortical glutamatergic synapses, but also in rare and much less understood synapse populations such as neuromodulatory dopamine synapses.

To tackle these issues, we combine two types of expertise mastered by the researchers of the team, myself and Etienne Herzog. I bring electrophysiology combined with the most advanced fluorescence imaging techniques to detect and characterize individual exocytosis and endocytosis events in living cells, while Etienne brings his method of purification of synaptosomes from adult animals with fluorescence activated synaptosome sorting which enables powerful proteomics, transcriptomics and functional approaches. Altogether we aim at identifying new principles of organization in specific synapses and test their relevance for synaptic function in the normal and diseased brain.

The members of the team being formed in January 2020 are Lou Bouit, Silvia Sposini, Marlene Pfeffer, Etienne Herzog, May Bakr and David Perrais.

- More details on the Bordeaux Neurocampus website here.
- Contact: David Perrais

eLife, April 2020

Optogenetic control of excitatory post-synaptic differentiation through neuroligin-1 tyrosine phosphorylation.
Neuroligins (Nlgns) are adhesion proteins mediating trans-synaptic contacts in neurons. However, conflicting results around their role in synaptic differentiation arise from the various techniques used to manipulate Nlgn expression level. Orthogonally to these approaches, we triggered here the phosphorylation of endogenous Nlgn1 in CA1 mouse hippocampal neurons using a photoactivatable tyrosine kinase receptor (optoFGFR1). Light stimulation for 24 hr selectively increased dendritic spine density and AMPA-receptor-mediated EPSCs in wild-type neurons, but not in Nlgn1 knock-out neurons or when endogenous Nlgn1 was replaced by a non-phosphorylatable mutant (Y782F). Moreover, light stimulation of optoFGFR1 partially occluded LTP in a Nlgn1-dependent manner. Combined with computer simulations, our data support a model by which Nlgn1 tyrosine phosphorylation promotes the assembly of an excitatory post-synaptic scaffold that captures surface AMPA receptors. This optogenetic strategy highlights the impact of Nlgn1 intracellular signaling in synaptic differentiation and potentiation, while enabling an acute control of these mechanisms.

Authors: Letellier M, Lagardère M, Tessier B, Janovjak H, Thoumine O.

- Publication on Elife. 2020 Apr 23;9. pii: e52027. doi: 10.7554/eLife.52027.
- Contacts: Mathieu Letellier and Olivier Thoumine
+ Cf Bordeaux Neurocampus website here

Astrocytic calcium signals can be fast and local, supporting the idea that astrocytes have the ability to regulate single synapses. However, the anatomical basis of such specific signaling remains unclear, owing to difficulties in resolving the spongiform domain of astrocytes where most tripartite synapses are located. Using 3D-STED microscopy in living organotypic brain slices, we imaged the spongiform domain of astrocytes and observed a reticular meshwork of nodes and shafts that often formed loop-like structures. These anatomical features were also observed in acute hippocampal slices and in barrel cortex in vivo. The majority of dendritic spines were contacted by nodes and their sizes were correlated. FRAP experiments and calcium imaging showed that nodes were biochemical compartments and Ca²⁺ microdomains. Mapping astrocytic calcium signals onto STED images of nodes and dendritic spines showed they were associated with individual synapses. Here, we report on living nanoscale organization of astrocytes, identifying nodes as a functional astrocytic component of tripartite synapses that may enable synapse-specific communication between neurons and astrocytes.

Misa Arizono et al in Nature Communications (2020)

The French Academy of Sciences provides links to find reliable information on the COVID-19 Coronavirus epidemic.

Our lab has closed down to allow the personnel to go under confinement and protection. A handful of dedicated members is taking care of our precious biological samples and mouse colonies. 

A major function of GPCRs is to inhibit presynaptic neurotransmitter release, requiring ligand-activated receptors to couple locally to effectors at terminals. The current understanding of how this is achieved is through receptor immobilization on the terminal surface. Here, we show that opioid peptide receptors, GPCRs that mediate highly sensitive presynaptic inhibition, are instead dynamic in axons. Opioid receptors diffuse rapidly throughout the axon surface and internalize after ligand-induced activation specifically at presynaptic terminals. We delineate a parallel regulated endocytic cycle for GPCRs operating at the presynapse, separately from the synaptic vesicle cycle, which clears activated receptors from the surface of terminals and locally reinserts them to maintain the diffusible surface pool. We propose an alternate strategy for achieving local control of presynaptic effectors that, opposite to using receptor immobilization and enforced proximity, is based on lateral mobility of receptors and leverages the inherent allostery of GPCR-effector coupling.

Damien Jullié, Miriam Stoeber, Jean-Baptiste Sibarita, Hanna L. Zieger, Thomas M. Bartol, Seksiri Arttamangkul, Terrence J. Sejnowski, Eric Hosy, and Mark von Zastrow

- Neuron. 2019 Dec 5 - doi: 10.1016/j.neuron.2019.11.016.
- Contact: Eric Hosy